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Kouki Oka

Section

Institute of Multidisciplinary Research for Advanced Materials

Job title

Associate Professor

Degree

博士（工学）（早稲田大学）

researchmap

https://researchmap.jp/k.oka

J-GLOBAL ID

202101006099935776

e-Rad No.

50907376

Research History 16

2025/04 - Present

Tohoku University　Graduate School of Engineering
2025/04 - Present

Tohoku University　Graduate School of Science
2025/04 - Present

Tohoku University　Institute of Multidisciplinary Research for Advanced Materials　Associate Professor
2024/05 - Present

茨城大学カーボンリサイクルエネルギー研究センター　特命研究員（兼任）
2024/04 - Present

京都大学学際融合教育推進センター重水素学研究拠点ユニットメンバー(兼任)
2021/12 - Present

早稲田大学早稲田高等学院　招聘講師（兼任）
2024/04 - 2025/03

University of Yamanashi
2024/04 - 2025/03

東北大学　大学院理学研究科化学専攻　講師（兼任）
2024/04 - 2025/03

Tohoku University　Graduate School of Engineering
2023/12 - 2025/03

Tohoku University　Institute of Multidisciplinary Research for Advanced Materials　Lecturer
2021/12 - 2023/11

大阪大学大学院工学研究科応用化学専攻　テニュアトラック助教
2021/12 - 2023/11

Osaka University　Assistant Professor, tenure track
2021/10 - 2021/11

Japan Society for the Promotion of Science　JSPS Cross-border Postdoctoral Research Fellow (CPD)
2021/04 - 2021/09

Japan Society for the Promotion of Science　JSPS Postdoctoral Research Fellow (PD)
2019/04 - 2021/03

Japan Society for the Promotion of Science　JSPS Research Fellow (DC1)
2018/10 - 2021/03

Uppsala University

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Education 1

Waseda University　Graduate School of Advanced Science and Engineering

2017/04 - 2021/03

Committee Memberships 7

⼀般社団法⼈触媒学会水素の製造と利用のための触媒技術研究会　世話人

2025/04 - Present
公益財団法人化学工学会　セッションオーガナイザー

2024/09 - Present
一般社団法人日本接着学会　若手交流シンポジウム代表世話人

2024/06 - Present
一般社団法人日本接着学会　若手交流会幹事

2024/06 - Present
公益財団法人高分子学会関西若手会　幹事

2022/01 - Present
公益社団法人高分子学会高分子未来塾　委員（レンジャー）

2021/07 - Present
日本学術振興会育志会（育志賞受賞者の会）　幹事

2021/04 - Present

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Professional Memberships 7

日本接着学会

2024/04 - Present
日本MRS水素科学技術連携研究会
触媒学会
日本学術振興会育志会
日本学術振興会スウェーデン日本人研究者の会
高分子学会
日本化学会

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Research Interests 4

機能性有機材料
エネルギー変換
高分子化学
電気化学

Research Areas 3

Nanotechnology/Materials / Organic functional materials /
Nanotechnology/Materials / Energy chemistry /
Nanotechnology/Materials / Polymer materials /

Awards 42

日本接着学会令和7年度（第47回）奨励賞

2025/06　一般社団法人日本接着学会
第24回インテリジェント・コスモス奨励賞

2025/05　公益財団法人インテリジェント・コスモス学術振興財団
小澤・吉川記念賞

2025/03　小澤・吉川記念エレクトロニクス研究助成基金
第30回青葉工学研究奨励賞

2024/11　一般社団法人青葉工学振興会
第12回研究部共同利用・共同研究若手萌芽研究最優秀賞

2024/05　東北大学金属材料研究所
第12回新化学技術研究奨励賞

2023/05　公益社団法人新化学技術推進協会
船井研究奨励賞

2023/03　公益財団法人船井情報科学振興財団
Inoue Research Award for Young Scientists

2022/12
研究奨励賞

2022/12　公益財団法人高柳健次郎財団
第16回わかしゃち奨励賞優秀賞

2021/12　愛知県
小野梓記念学術賞

2021/03　早稲田大学
第11回（令和2（2020）年度）日本学術振興会育志賞

2021/01
最優秀発表賞

2020/04　超異分野学会本大会
ナノアカデミア賞

2020/01　nano tech 2020
ハイドロジェノミクス奨励賞

2019/11　新学術領域研究ハイドロジェノミクス
感謝状

2024/11　早稲田大学高等学院
太陽誘電賞

2024/11　東北テックプラングランプリ2024
Best Researcher Award

2024/06　International Research Awards on Leadership and Management
ONSA賞

2024/05　（一社）大阪ニュークリアサイエンス協会
感謝状

2023/11　早稲田大学高等学院
大阪大学賞

2023/10　国立大学法人大阪大学
Journal of Materials Chemistry A, HOT Papers

2023/04　The Royal Society of Chemistry　Redox-site accessibility of composites containing a 2D redox-active covalent organic framework: from optimization to application
感謝状

2023/03　早稲田大学高等学院
1st in Academic Researcher (Finalist),

2022/10　Genius Challenge (Iodine Innovation) by SQM
第54回リバネス研究費日本ハム賞

2022/03
感謝状

2021/12　公益社団法人高分子学会高分子未来塾委員会
大倉工業賞

2021/12　超異分野学会香川フォーラム
感謝状

2021/10　株式会社リバネス
Polymer Journal highlight article

2021/07
感謝状

2021/07　公益財団法人高分子学会
スウェーデン･ウプサラ大学博士課程ジョイントスーパービジョンプログラム修了

2021/03
土田英俊先生記念奨学金

2021/03　早稲田大学高研会
水野賞

2021/03　早稲田大学
第49回リバネス研究費ダスキン開発研究所賞

2021/02
第1回エコテックグランプリ_ファイナリスト選出

2020/10
第46回リバネス研究費エネルギー・エコシステム賞

2020/01
Best Poster Award

2020/01　14th INTERNATIONAL SYMPOSIUM HYDROGEN & ENERGY
最優秀ポスター賞

2019/12　未来・水素エネルギーフォーラム
Gold Award

2019/10　6th Federation of Asian Polymer Societies International Polymer Congress
S評価 (最高評価)

2019/03　早稲田大学アドバイザリーボード（企業執行役員からの研究評価）
優秀ポスター賞

2017/09　第66回高分子討論会
Poster Presentation Award

2017/08　17th IUPAC International Symposium on MacroMolecular Complexes

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Papers 92

Iodine-Based Chemical Polymerization Enables the Development of Neat Amorphous Porous Organic Polymers Peer-reviewed

Kohei Okubo, Haruka Yoshino, Hitoshi Miyasaka, Hitoshi Kasai, Kouki Oka

ACS Applied Materials & Interfaces　2025/02/21
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acsami.4c22197 　

ISSN： 1944-8244

eISSN： 1944-8252
Triphenylamine‐Based Porous Organic Polymers with High Porosity: their High Carbon‐Dioxide Adsorption and Proton‐Conductivity Emergence Peer-reviewed

Kohei Okubo, Showa Kitajima, Hitoshi Kasai, Kouki Oka

Small　2025/02/17
Publisher: Wiley
DOI： 10.1002/smll.202410794 　

ISSN： 1613-6810

eISSN： 1613-6829

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Abstract Amorphous porous organic polymers (POPs) feature high specific surface area and chemical and thermal stability; therefore, they are applied in various fields. It is previously reported that chemical polymerization using iodine as an oxidant enables the synthesis of amorphous POPs without impurities. In this study, an iodine‐based chemical polymerization method is employed to maximize the specific surface area of polytriphenylamine, a typical amorphous POP. Furthermore, 1,3,5‐tris[4‐(diphenylamino)phenyl]benzene, a monomer with three triphenylamine moieties connected by a benzene core, is used to increase the number of reaction points and construct a rigid structure. The resulting poly[1,3,5‐tris[4‐(diphenylamino)phenyl]benzene] (pTTPA) exhibited a high specific surface area. Using 200 equivalents of iodine resulted in a pTTPA with the largest Brunauer–Emmett–Teller (BET) specific surface area (2134.6 m² g⁻¹) among previously reported triphenylamine‐based amorphous POPs, and demonstrated a high CO₂ adsorption capacity (3.31 mmol g⁻¹ at 25 °C). Furthermore, pTTPA exhibited significant water–vapor adsorption when the BET specific surface area reached 1500 m² g⁻¹, leading to the emergence of proton conductivity (e.g., 4.33 × 10⁻⁶ S cm⁻¹ at 95% RH and 90 °C). The findings demonstrate that iodine‐based chemical polymerization enables the maximization of the porosity of amorphous POPs and the development of proton conductivity within them.
Sustainable hydrogen production & storage cycle with dihydrolevoglucosenone (Cyrene™): Hydrogen fixing and release based on alcoholic fermentation with Baker's yeast and dehydrogenation Peer-reviewed

Takumi Ichimura, Hiroki Maeda, Takuya Shimbayashi, Kohei Okubo, Masayuki Fukushima, Norimitsu Tohnai, Ken-ichi Fujita, Kouki Oka

International Journal of Hydrogen Energy　72　815-819　2024/06/28
Publisher: Elsevier BV
DOI： 10.1016/j.ijhydene.2024.05.403 　

ISSN： 0360-3199
Highly Fluorinated Nanospace in Porous Organic Salts with High Water Stability/Capability and Proton Conductivity Peer-reviewed

Takahiro Ami, Showa Kitajima, Kouki Oka, Norimitsu Tohnai

Angewandte Chemie International Edition　2024/06/20
Publisher: Wiley
DOI： 10.1002/anie.202407484 　

ISSN： 1433-7851

eISSN： 1521-3773

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Water in hydrophobic nanospaces shows specific dynamic properties different from bulk water. The investigation of these properties is important in various research fields, including materials science, chemistry, and biology. The elucidation of the correlation between properties of water and hydrophobic nanospaces requires nanospaces covered only with simple hydrophobic group (e.g., fluorine) without impurities such as metals. This work successfully fabricated all‐organic diamondoid porous organic salts (d‐POSs) with highly fluorinated nanospaces, wherein hydrophobic fluorine atoms are densely exposed on the void surfaces, by combining fluorine substituted triphenylmethylamine (TPMA) derivatives with tetrahedral tetrasulfonic acid. This d‐POSs with a highly fluorinated nanospace significantly improved their water stability, retaining their crystal structure even when immersed in water over one week. Moreover, this highly hydrophobic and fluorinated nanospace adsorbs 160 mL(STP)/g of water vapor at Pe/P0 = 0.90; this is the first hydrophobic nanospace, which water molecules can enter, in an all‐organic porous material. Furthermore, this highly fluorinated nanospace exhibits very high proton conductivity (1.34 × 10−2 S/cm) at 90°C and 95%RH. POSs with tailorable nanospaces may significantly advance the elucidation of the properties of specific “water” in pure hydrophobic environments.
Spirobifluorene‐Based Porous Organic Salts: Their Porous Network Diversification and Construction of Chiral Helical Luminescent Structures Peer-reviewed

Kohei Okubo, Kouki Oka, Keiho Tsuchiya, Atsunori Tomimoto, Norimitsu Tohnai

Angewandte Chemie International Edition　2024/01/27
Publisher: Wiley
DOI： 10.1002/anie.202400475 　

ISSN： 1433-7851

eISSN： 1521-3773

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Porous organic salts (POSs) are organic porous materials assembled via charge‐assisted hydrogen bonds between strong acids and bases such as sulfonic acids and amines. To diversify the network topology of POSs and extend its functions, this study focused on using 4,4',4'',4'''‐(9,9'‐spirobi[fluorene]‐2,2',7,7'‐tetrayl)tetrabenzenesulfonic acid (spiroBPS), which is a tetrasulfonic acid comprising a square planar skeleton. The POS consisting of spiroBPS and triphenylmethylamine (TPMA) (spiroBPS/TPMA) was constructed from the two‐fold interpenetration of an orthogonal network with pts topology, which has not been reported in conventional POSs, owing to the shape of the spirobifluorene backbone. Furthermore, combining tris(4‐chlorophenyl)methylamine (TPMA‐Cl) and tris(4‐bromophenyl)methylamine (TPMA‐Br), which are bulkier than TPMA owing to the introduction of halogens at the p‐position of the phenyl groups with spiroBPS allows us to construct novel POSs (spiroBPS/TPMA‐Cl and spiroBPS/TPMA‐Br). These POSs were constructed from a chiral helical network with pth topology, which was induced by the steric hindrance between the halogens and the curved fluorene skeleton. Moreover, spiroBPS/TPMA‐Cl with pth topology exhibited circularly polarized luminescence (CPL) in the solid state, which has not been reported in hydrogen‐bonded organic frameworks (HOFs).
Porous Organic Salts: Diversifying Void Structures and Environments Peer-reviewed

Takahiro Ami, Kouki Oka, Keiho Tsuchiya, Norimitsu Tohnai

Angewandte Chemie International Edition　61　(31)　2022/05/19
Publisher: Wiley
DOI： 10.1002/anie.202202597 　

ISSN： 1433-7851

eISSN： 1521-3773
Organic π‐Conjugated Polymers as Photocathode Materials for Visible‐Light‐Enhanced Hydrogen and Hydrogen Peroxide Production from Water Peer-reviewed

Kouki Oka, Bjorn Winther‐Jensen, Hiroyuki Nishide

Advanced Energy Materials　11　(43)　2003724-2003724　2021/11
Publisher: Wiley
DOI： 10.1002/aenm.202003724 　

ISSN： 1614-6832

eISSN： 1614-6840
Poly(1,4‐di(2‐thienyl))benzene Facilitating Complete Light‐Driven Water Splitting under Visible Light at High pH Peer-reviewed

Kouki Oka, Kanako Noguchi, Takeo Suga, Hiroyuki Nishide, Bjorn Winther‐Jensen

Advanced Energy Materials　9　(6)　1803286-1803286　2019/02
Publisher: Wiley
DOI： 10.1002/aenm.201803286 　

ISSN： 1614-6832

eISSN： 1614-6840
Poly(vinyldibenzothiophenesulfone): Its Redox Capability at Very Negative Potential Toward an All‐Organic Rechargeable Device with High‐Energy Density Peer-reviewed

Kouki Oka, Ryo Kato, Kenichi Oyaizu, Hiroyuki Nishide

Advanced Functional Materials　28　(50)　1805858-1805858　2018/12
Publisher: Wiley
DOI： 10.1002/adfm.201805858 　

ISSN： 1616-301X

eISSN： 1616-3028
Light-assisted electrochemical water-splitting at very low bias voltage using metal-free polythiophene as photocathode at high pH in a full-cell setup Peer-reviewed

Kouki Oka, Orie Tsujimura, Takeo Suga, Hiroyuki Nishide, Bjorn Winther-Jensen

Energy and Environmental Science　11　(5)　1335-1342　2018/05

DOI： 10.1039/c7ee03669h 　

ISSN： 1754-5692

eISSN： 1754-5706
Cytotoxicity Study of π‐Conjugated Arsenic Compounds Peer-reviewed

Tomoki Yasui, Aki Shibata, Tomoka Ishikawa, Yukako Fujita, Chihiro Okochi, Yoshitaka Koseki, Hitoshi Kasai, Kouki Oka, Kensuke Naka, Hiroaki Imoto

ChemistrySelect　10　(21)　2025/06/03
Publisher: Wiley
DOI： 10.1002/slct.202502502 　

ISSN： 2365-6549

eISSN： 2365-6549

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Abstract Organoarsenic chemistry is an emerging field focused on the development of heteroatom‐containing functional organic materials. However, concerns regarding the potential toxicity of arsenic remain to be addressed. In this study, we evaluated the cytotoxicity of π‐conjugated organoarsenic compounds against HCT‐116 human colon cancer cells using a nanoparticle fabrication method. Various functional organoarsenic compounds exhibited low‐to‐negligible cytotoxicity (IC₅₀ > 10 µM), in contrast to phenylarsine oxide (IC₅₀ = 2.8 µM), a compound well‐known for its high toxicity. Notably, phenylarsonic acid, a key synthetic precursor of these compounds, also demonstrated very low cytotoxicity.
Front Cover: Recyclable Organic Redox Molecules for Sustainable Batteries (ChemSusChem 11/2025)

Kouki Oka, Hitoshi Kasai

ChemSusChem　18　(11)　2025/06/02
Publisher: Wiley
DOI： 10.1002/cssc.202581101 　

ISSN： 1864-5631

eISSN： 1864-564X
Rechargeable organic molecule-air battery Peer-reviewed

Showa Kitajima, Ryota Tanaka, Takumi Ichimura, Hitoshi Kasai, Kensuke Naka, Norimitsu Tohnai, Hiroaki Imoto, Kouki Oka

Cell Reports Physical Science　102620-102620　2025/06
Publisher: Elsevier BV
DOI： 10.1016/j.xcrp.2025.102620 　

ISSN： 2666-3864
Hydrogen gas production & storage cycle with organic hydrides based on hydrogen fixing and release Invited Peer-reviewed

Takumi Ichimura, Hitoshi Kasai, Kouki Oka

Energy 360　3　100028-100028　2025/06
Publisher: Elsevier BV
DOI： 10.1016/j.energ.2025.100028 　

ISSN： 2950-4872
Hydrophilization of Guaiazulene-based Blue Pigment: Improving its Stability in Acidic Condition by Substitution with Polyallylamine Peer-reviewed

Yo Kinoshita, Kiyotaka Maruoka, Yuta Takahashi, Yoko Teruchi, Minoru Takeuchi, Kazuhiko Igarashi, Hitoshi Kasai, Kouki Oka

New Journal of Chemistry　2025/05
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d5nj01214g 　

ISSN： 1144-0546

eISSN： 1369-9261

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Guaiazulene, an azulene compound with a blue color more saturated than that of naturally derived blue pigments, shows potential as a food coloring agent. However, poor water solubility and loss...
Recyclable Organic Redox Molecules for Sustainable Batteries Peer-reviewed

Kouki Oka, Hitoshi Kasai

ChemSusChem　2025/03/18
Publisher: Wiley
DOI： 10.1002/cssc.202402707 　

ISSN： 1864-5631

eISSN： 1864-564X

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Sustainable and environment‐friendly rechargeable devices are required to meet increasing electrical energy demands. Organic batteries are fabricated using organic redox materials which are potentially synthesised from earth‐abundant components. However, to avoid plastic pollution, these organic materials must display sufficient functions and ensure safe management post‐utilisation. This study demonstrated a sustainable and environment‐friendly recycling method for functional organic materials developed using organic redox molecules. These molecules could be prepared from earth‐abundant and sustainable raw chemicals via environment‐friendly preparation routes. The eco‐friendly battery, which uses organic redox molecules as anode‐ and cathode‐active materials and neutral aqueous solution as an electrolyte, exhibited high cyclability (>95% capacity after 100 cycles) and high‐rate capability (15 C). After use, the electrode‐active material was separated and/or decomposed to the original raw chemicals, demonstrating a green and sustainable option to use conventional organic redox materials.
Dihydrolevoglucosenone (CyreneTM) as a Bio‐derived Liquid Organic Hydrogen Carrier Invited Peer-reviewed

Takumi Ichimura, Hitoshi Kasai, Kouki Oka

ChemPlusChem　2025/01/03
Publisher: Wiley
DOI： 10.1002/cplu.202400639 　

ISSN： 2192-6506

eISSN： 2192-6506

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Organic hydrides can store hydrogen via chemical bonding under ambient conditions, enabling the safe storage and transportation of hydrogen gas using the same infrastructure for gasoline. However, in previous research, most organic hydrides have been produced from petroleum, and therefore replacing them with earth‐abundant or renewable compounds is essential to ensure sustainability. This study demonstrates dihydrolevoglucosenone (CyreneTM), which is a biodegradable liquid ketone that is produced directly from biomass without pretreatments on an industrial scale, as a new renewable organic hydride. CyreneTM (hydrogen acceptor) is hydrogenated under ambient hydrogen pressure with a highly durable metal complex catalyst to produce 1,6‐anhydro‐3,4‐dideoxy‐β‐D‐threo‐hexopyranose (Cyrene‐OH, hydrogen adduct). Cyrene‐OH stores hydrogen via chemical bonding under ambient conditions, and is dehydrogenated by heating in the presence of the same catalyst to release hydrogen gas and reproduce CyreneTM. This study reports the first attempt to apply compounds, which can be produced directly from biomass on an industrial scale, to organic hydrides, and promotes the development of earth‐abundant biomass for sustainable hydrogen storage.
Fluorinated Metal–Organic Frameworks: Hydrophobic Nanospaces with High Fluorine Density and Proton Conductivity Peer-reviewed

Ryota Akai, Hitoshi Kasai, Kouki Oka

Nanoscale　2025
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d5nr00342c 　

ISSN： 2040-3364

eISSN： 2040-3372

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The current work revealed the relationship between the fluorine density of organic-based porous materials and water dynamics (proton conduction) in the hydrophobic nanospace. In detail, focusing on UiO-66 with structural...
Front cover

Kouki Oka

Chemical Communications　61　(8)　1473-1473　2025/01
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d5cc90031j 　

ISSN： 1359-7345

eISSN： 1364-548X
Developing porous electrocatalysts to minimize overpotential for the oxygen evolution reaction Invited Peer-reviewed

Takahiro Ami, Kouki Oka, Hitoshi Kasai, Tatsuo Kimura

Chemical Communications　61　(8)　1533-1558　2025/01
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d4cc05348f 　

ISSN： 1359-7345

eISSN： 1364-548X

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This feature article mainly outlines the advances in the precise design of inorganic- and organic-based porous electrocatalysts towards the enhancement of oxygen evolution reaction (OER) properties to achieve efficient water-splitting reaction.
Hydrophilization of hydrophobic azulene derivative by substitution with polyallylamine without drastically changing its optical properties Peer-reviewed

Yo Kinoshita, Kiyotaka Maruoka, Yuta Takahashi, Yoko Teruuchi, Minoru Takeuchi, Kazuhiko Igarashi, Hitoshi Kasai, Kouki Oka

MRS Communications　2024/11/25
Publisher: Springer Science and Business Media LLC
DOI： 10.1557/s43579-024-00680-y 　

eISSN： 2159-6867
An SEI-Forming Fluorophosphate Solvent for High-Temperature Lithium-Ion Batteries Peer-reviewed

Kazuki Takeuchi, Yasuyuki Kondo, Yu Katayama, Kouki Oka, Yuki Yamada

ECS Meeting Abstracts　MA2024-02　(67)　4533-4533　2024/11/22
Publisher: The Electrochemical Society
DOI： 10.1149/ma2024-02674533mtgabs 　

eISSN： 2151-2043

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Introduction Recently, there has been an increasing demand for high-energy-density lithium-ion batteries (LIBs) that operate under broad temperature conditions (–40 to 70°C). As an electrolyte solvent, ethylene carbonate (EC) has been essential to form a solid electrolyte interphase (SEI), which effectively suppresses side reactions such as graphite exfoliation and continuous electrolyte decomposition on negative electrodes⁽¹⁾. However, EC is not only flammable but also susceptible to severe oxidative and reductive decomposition at high temperatures, thereby limiting the operational temperature of LIBs to around 55°C⁽²⁾. There has been no alternative solvent that has (i) SEI-forming ability, (ii) nonflammability, and (iii) high-temperature stability. Hence, it has been challenging to realize the high-temperature and safe operation of LIBs. In this study, we designed and synthesized a novel phosphate solvent, FDPO, which is nonflammable and can form stable SEI on graphite. FDPO has a structural feature similar to LiPO₂F₂, which can improve SEI properties and high-temperature performance of batteries^(3-4). We investigated the charge-discharge performances of negative and positive electrodes for LIBs with FDPO-based electrolytes at high temperature. Experimental methods Electrolytes were prepared by mixing LiPF₆, FDPO, and methyl 2,2,2-trifluoroethyl carbonate (FEMC), which is known as a low viscous and flame-retardant solvent. Charge-discharge tests were conducted using coin cells with the natural graphite|Li cell configuration. The current density of 186 mA g^-1 (2C) was applied from the 4th cycle after pre-conditioning three cycles at a current density of 37.2 mA g^-1 (10C). The cut-off voltage range was set to 2.5 V – 0.01 V. Results and discussion Figure 1 shows the charge-discharge performances of natural graphite|Li coin cells at 70°C. The cell with the commercial electrolyte exhibited severe capacity decay to ca. 142 mAh g^-1 after 50th cycles. On the other hand, the cell with FDPO-based electrolyte retained a high reversible capacity of ca. 343 mAh g^-1. In addition, the charge-discharge efficiency was over 99.6% in the FDPO-based electrolyte, indicating suppressed electrolyte decomposition even at 70°C. Based on these results, the FDPO itself is thermally stable and also forms a thermally stable SEI on graphite, thereby suppressing capacity degradation under high-temperature conditions. In the presentation, the results of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses for the SEI derived from FDPO-based electrolytes, along with the charge-discharge performances of positive electrodes, will be discussed. References (1) Wang, A. et al., npj Computational Materials, 2018, 4, 15. (2) Lu, L. et al., J. Power Sources, 2013, 226, 272. (3) Yang, G. et al., RSC Adv, 2017, 7, 26052. (4) Kuang, S. et al., ACS Appl. Mater. Interfaces, 2022, 14, 19056-19066. Acknowledgment A part of this work was supported by JST GteX (JPMJGX23S3). Figure 1
Organic π-Conjugated Polymers as a Photoelectrocatalyst for Water-Splitting Peer-reviewed

Kouki Oka

ECS Meeting Abstracts　MA2024-02　(59)　3951-3951　2024/11/22
Publisher: The Electrochemical Society
DOI： 10.1149/ma2024-02593951mtgabs 　

eISSN： 2151-2043

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Introduction Hydrogen gas (H₂ ) is an important chemical feedstock; it is used as a reductant in petroleum refining, ammonia synthesis, the manufacture of stainless steel, and the production of core chemicals (e.g., methanol) and food (e.g., margarine). H₂ is also regarded to be a critical and indispensable clean fuel for sustainable energy systems because of its extremely high energy density of 142 kJ g⁻¹ (vs. 44 kJ g⁻¹ for gasoline) and low pollution emissions.¹⁾ However, H₂ is presently produced by conversion of hydrocarbons or fossil fuels and is accompanied by enormous energy consumption and greenhouse gas emissions. To realize carbon neutral and sustainable circulation technology, carbon-free and green H₂ production methods, such as water-splitting, are required.²⁾ Results and discussion This presentation describes organic π-conjugated polymers as a novel photoelectrocatalyst towards water-splitting.^2-4) π-Conjugated polymers synthesized without residual metals were developed to function in "water", which defied common sense, leading to this novel catalytic ability. In detail, (1) we succeeded in synthesizing polythiophene, which is a type of π-conjugated polymer, in a film form without residual metal by our unique iodine-vapor-phase polymerization method (2) We found that this polythiophene film worked as a novel photoelectrocatalyst that absorbs visible-light and highly efficiently reduces water to generate H₂ . (3) In addition, based on a rigid π-conjugated polymer structure, this polythiophene film catalyzed water-splitting/ H₂ production with surprisingly high durability (more than 1 month without no degradation). The development of environmentally-friendly organic catalysts that do not use precious metals will lead to the production of truly green H₂ . We will also describe developments to other catalytic functions (O₂ reduction/ H₂O₂ production etc.) of organic π-conjugated polymers. References 1) Schlapbach, L. et al., Nature, 2001, 414, 353-358. 2) Oka, K. et al., Adv. Energy Mater., 2021, 11, 2003724. 3) Oka, K. et al., Energy Environ. Sci., 2018, 11, 1335-1342. 4) Oka, K. et al., Adv. Energy Mater. 2019, 9, 1803286. Acknowledgment This work was partially supported by Grants-in-Aids for Scientific Research (No. JP23K17945, JP23H03827, JP24K01552) from MEXT, Japan. K. Oka. also acknowledges the support from Shorai Foundation for Science and Technology, TEPCO Memorial Foundation, Amano Industry Technology Laboratory, Sugiyama Houkoukai, The Yamada Science Foundation, Kenjiro Takayanagi Foundation, Kansai Research Foundation for Technology Promotion, and JACI Prize for Encouraging Young Researcher.
Rechargeable Organic Molecule-Air Battery Peer-reviewed

Showa Kitajima, Hitoshi Kasai, Kouki Oka

ECS Meeting Abstracts　MA2024-02　(67)　4464-4464　2024/11/22
Publisher: The Electrochemical Society
DOI： 10.1149/ma2024-02674464mtgabs 　

eISSN： 2151-2043

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[Introduction] The development of environmentally friendly batteries, such as rechargeable aqueous metal-air batteries, has been required for sustainable energy supply. Aqueous zinc-air batteries, composed of zinc as the anode, O₂ in the air as the cathode, and a very base aqueous solution (e.g., 6 M KOH aqueous solution) as the electrolyte, are one of the representative environmentally friendly batteries, because of their high energy density (1353 W h kg⁻¹ excluding oxygen) compared to conventional lithium-ion batteries (limited to be <350 W h kg⁻¹ based on the intercalation chemistry).[1] However, these batteries usually have extremely low cyclability because of dendrite formation on the anode and carbonate salt clogging (i.e., the reaction between CO₂ in the air and the base) in the electrolyte during charging and discharging. To improve their cyclability, we previously reported a rechargeable organic polymer-air battery using a redox polymer with an anthraquinone derivative (which has a one-step two-electron redox capability in an acidic aqueous solution).[2] This rechargeable organic polymer-air battery exhibits a very high Coulombic efficiency of 99% because of the distorted structure of the anthraquinone derivative. However, organic redox polymers with linear polymer structures are not sufficiently robust for long-term use as an anode-active material in aqueous air batteries. On the other hand, Prof. Yu et al. have recently fabricated a rechargeable organic polymer-air battery using a networked polymer based on anthraquinone as an anode-active material and demonstrated very high cyclability of presumably 99% capacity retention even after 60,000 cycles.[3] This is presumably because the networked polymer forms a robust three-dimensional network that prevents it from decomposing or dissociating from the electrode. However, the Coulombic efficiency was lower than that of organic polymer-air batteries with organic linear polymers, and was only 95%. To achieve both the sufficiently high cyclability and high Coulombic efficiency as an aqueous air battery, the anode-active material must possess high hydrophilicity, exhibit high diffusivity of compensating ions in the material, and have a robust structure that is not decomposed or dissociated from the electrode during charging and discharging. In this work, as the anode-active material, we focused on the anthraquinone molecule itself, which has a reversible redox capacity at the very negative potential close to the potential window in aqueous electrolytes and whose redox properties can be modulated by facile organic synthesis. To improve anthraquinone’s hydrophilicity and inhibit its aggregation, we synthesized 2-propoxyethyl anthraquinone-2-carboxylate. 2-propoxyethyl anthraquinone-2-carboxylate had a reversible redox potential in an acidic aqueous solution, and we established a novel rechargeable organic molecule-air battery using2-propoxyethyl anthraquinone-2-carboxylate as the anode-active material and an acidic aqueous solution as the electrolyte. [Results & Discussions] The battery was chargeable and dischargeable, with the very high Coulombic efficiency of >99% at 15 C. The discharge capacity was almost full capacity, indicating that almost all the molecules contributed to charging and discharging. The discharge capacity remained >99% even after 100 cycles, indicating that the battery had a very high cyclability. Even at 60 C, the discharge capacity of the battery was almost the same as that at 15 C, indicating a high-rate capability. Moreover, the results confirm that this novel rechargeable organic molecule-air battery exhibits the highest cyclability and Coulombic efficiency in rechargeable organic-based aqueous air batteries. Using 2-propoxyethyl anthraquinone-2-carboxylate as an anode-active material in aqueous air batteries will potentially achieve almost the same energy density and increase power density by several times or more, compared to the polymer-air batteries demonstrated. Therefore, the energy density of the aqueous air battery using 2-propoxyethyl anthraquinone-2-carboxylatewill be almost the same as that of metal-air batteries (e.g., zinc-air batteries), and its power density is expected to be higher than that of lithium-ion batteries. We want to discuss this in more detail at the poster session. [Reference] [1] J. Zhang et al., Chem. Sci. 2019, 10, 8924-8929. [2] K. Oka et al., Macromolecules 2021, 54, 4854-4859. [3] L. Zhong et al., Angew. Chem. Int. Ed. 2021, 60, 10164-10171. Figure 1
Weakly Coordinating Solvents with FSI-Inspired Structures for Highly Efficient Lithium Metal Batteries Peer-reviewed

Shoma Nishimura, Yasuyuki Kondo, Kazuki Takeuchi, Yu Katayama, Kouki Oka, Yuki Yamada

ECS Meeting Abstracts　MA2024-02　(7)　997-997　2024/11/22
Publisher: The Electrochemical Society
DOI： 10.1149/ma2024-027997mtgabs 　

eISSN： 2151-2043

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１．Introduction Low Coulombic efficiency (CE) of lithium (Li) plating/stripping due to electrolyte decomposition on Li metal negative electrodes is a critical issue in the practical application of Li metal batteries. Our previous study^[1] revealed that increasing the concentration of lithium bis(fluorosulfonyl)imide (LiFSI) in organic electrolytes leads to a weakly coordinated environment of Li⁺ with FSI⁻, which increases Li⁺ chemical potential (µ _Li ⁺) and Li electrode potential (E _Li), thus minimizing electrolyte reductive decomposition and achieving high CEs. However, concentrated electrolytes have disadvantages such as high viscosity and high cost. Herein we focused on FSI-inspired solvents with a weakly Li⁺-coordinating structure of -NSO₂F.^[2][3] This class of solvents have been studied with a focus on their solid electrolyte interphase (SEI) forming ability similar to LiFSI,^[2][3]but there has been no understanding on the µ _Li ⁺ and E _Li in such solvents. We studied the E _Liand Li plating/stripping CE in various FSI-inspired solvents and discuss their correlation. ２．Experimental The electrolytes were prepared by dissolving LiFSI in FSI-inspired solvents (diMeFSI; N,N-dimethylsulfamoyl fluoride, EtMeFSI; N-ethyl, N-methylsulfamoyl fluoride, diEtFSI; N,N-diethylsulfamoyl fluoride), FEC; fluoroethylene carbonate, and DME; 1,2-dimethoxyethane at a LiFSI:solvent molar ratio of 1/8 (Figure 1.). A three-electrode cell was used for cyclic voltammetry (CV) with a Pt plate as the working electrode and Li foil as the counter and reference electrodes. Ferrocene (Fc, 1 mM) was dissolved in the electrolytes. E _Li was evaluated with reference to the redox potential of Fc as an internal standard. Cu|Li coin cells were used to evaluate Li plating/stripping CEs. Li was plated on Cu for 1 hour and stripped up to 0.5 V at a current density of 0.5 mA cm^- ². ３．Results & Discussion Figure 2. shows E _Li in various electrolytes with reference to Fc/Fc⁺. The E _Li values of FSI-inspired solvents were notably higher (-2.9 V vs. Fc/Fc⁺) than FEC or DME even at the same LiFSI:solvent molar ratios (1/8). This is due to the weakly Li⁺-solvating nature of the FSI^--inspired solvents, which was also supported by DFT calculations. Figure 3. shows the average Li plating/stripping CEs of 2~20 cycles in various electrolytes. For diMeFSI, EtMeFSI, diEtFSI, DME, and FEC, the LiFSI/solvent ratios were 1/8. The data of other various electrolytes (limited to salt concentrations below 2 M) are reproduced from our previous publication^[1] and shown as black dots. Among such dilute electrolytes, the highest E _Li (-2.92 V) and the highest CE can be both achieved in diMeFSI electrolytes. This suggests that introducing such an FSI structure into solvents is a promising way to not only forming a better FSI-derived SEI but also upshifting the E _Li for highly efficient Li metal anodes. 4 ．References [1] S. Ko et al., Nat. Energy, 7, 1217 (2022). [2] W. Xue et al., Energy Environ. Sci., 13, 212 (2020). [3] K. Jiang et al., ACS Energy Lett. 7, 3378 (2022). 5.Acknowledgement This work was partially supported by JSPS KAKENHI Grant-in-Aid for Transformative Research Areas (B) (23H03824, 23H03827). Figure 1
Redox-Active Metal-Organic Framework As an Anode-Active Material for Rechargeable Air Batteries Peer-reviewed

Ryota Akai, Hitoshi Kasai, Kouki Oka

ECS Meeting Abstracts　MA2024-02　(67)　4399-4399　2024/11/22
Publisher: The Electrochemical Society
DOI： 10.1149/ma2024-02674399mtgabs 　

eISSN： 2151-2043

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[Introduction] Rechargeable batteries for the storage of electrical energy are required for the introduction of renewable energy and compact electronic devices for the sustainable society.^[1] Although lithium-ion batteries currently dominate the market, rechargeable metal–air batteries with very high energy densities have been attracting attention due to increasing power consumption and demand for low environmental burden. They are composed of oxygen from air as the cathode-active material, metal as the anode-active material and a strong alkaline solution as the electrolyte. They have the advantage of high energy density and low environmental burden due to the use of oxygen as the cathode-active material. While primary Zn–air batteries are commercialized, rechargeable metal–air batteries are under investigation due to their low cycle performance caused by dendrites and metal oxides formed on the metal anode, which leads to disposal of anode-active materials. In addition, strong basic electrolytes are used due to their high ionic conductivity, and the carbonate clogging by carbon dioxide in the air is also a problem. Therefore, rechargeable air batteries, which consist of acid or neutral electrolyte and anode-active materials which is recyclable and do not form dendrites or metal oxides, are required. Organic redox molecules, which are reversibly redox-active organic compounds, are composed of earth-abundant and relatively available building blocks (C, H, N, O, and S), and their functions can be tuned by molecular design, which has attracted attention as new electrode-active materials. We have previously reported that rechargeable polymer–air batteries using an organic redox polymer with organic redox molecules in the side chain of polymer as the anode-active material and acidic aqueous solution as the electrolyte charged and discharged without the formation of dendrites or carbonates.^[2] However, organic materials suffer from low durability, and organic redox materials with structural stability in the electrolyte have been required. In the current work, we focused on UiO-66, a metal-organic framework with structural stability in acid and base electrolyte, and synthesized UiO-66-(OH₂) with 1,4-dihydroxybenzene, an organic redox molecule as a linker, which undergoes a reversible redox reaction even in acid electrolytes. An anode-active material composed of UiO-66-(OH₂) did not form dendrites or metal oxides in H₂SO₄ aqueous electrolyte (pH 1) and exhibited charge storage with high cycle stability. A rechargeable acidic MOF–air battery was demonstrated for the first time. After use, UiO-66-(OH₂) electrode was facilely decomposed and separated to the original raw chemicals by NH₄HCO₃ aqueous solution. [Results and Discussion] We synthesized UiO-66-(OH₂) from zirconium(IV) chloride and 2,5-dihydroxyterephthalic acid by microwave irradiation. UiO-66-(OH₂) was coated on a glassy carbon plate in the presence of single-walled carbon nanotube as the conductive additive. The UiO-66-(OH₂) electrode exhibited charging-discharging curves of a plateau voltage at 0.2 V, and the ratio of discharging vs. charging capacity (i.e. coulombic efficiency) were nearly 96%. The high capacity of the UiO-66-(OH₂) electrode suggested that almost all of the -OH moieties contributed to charge storage. Even after 300 cycles, UiO-66-(OH₂) electrode exhibited high cycle performance, which was relatively robust compared to other n-type redox materials for rechargeable aqueous air batteries. These results demonstrated that UiO-66-(OH₂) has high cycle stability as an anode-active material for rechargeable acidic MOF-air batteries. A rechargeable acidic MOF-air battery was fabricated with a UiO-66-(OH₂), Pt/C, and H₂SO₄ aqueous electrolyte (pH 1) as the anode material, cathode material, and electrolyte, respectively. The coulombic efficiencies of the battery were nearly 97%, demonstrating the reversible charge storage property of the cell. The high capacity for the anode suggested that almost all of the -OH moieties contributed to charge storage. Even after 100 charging-discharging cycles, the battery kept the high discharging capacity even at a rapid discharging. These results demonstrated the long-life ability of the rechargeable acidic MOF-air battery. UiO-66-(OH₂) electrode in the battery was facilely decomposed and separated to the original raw chemicals by NH₄HCO₃ aqueous solution after charging and discharging. [Conclusions] We synthesized UiO-66-(OH₂), which is stable in aqueous electrolyte, and applied it to an anode-active material. The rechargeable acidic MOF-air battery exhibited high cycle performance without the formation of dendrites or carbonates. In addition, we successfully recycled UiO-66-(OH₂) electrode after charging and discharging. The current work presented a first step for developing electrode materials for the future energy storage. [References] [1] J. Kim, Y. Kim, J. Yoo, G. Kwon, K. Kang et al., Nat. Rev. Mater. , 8, 54–70, 2023. [2] K. Oka, S. Furukawa, S. Murao, H. Nishide, K. Oyaizu et al., Chem. Commun. , 56, 4055–4058, 2020. Figure 1
Alkyl-Ether Group-Modified Anthraquinone-Based Negative Electrode for Enhanced Electrochemical Performance of All Solid-State Rechargeable Air Batteries Peer-reviewed

Lin Guo, Kenji Miyatake, Suguru Wada, Kouki Oka, Showa Kitajima, Hitoshi Kasai, Ryota Tanaka, Hiroaki Imoto, Kensuke Naka, Fang Xian, Fanghua Liu, Ahmed Mohamed Ahmed Mahmoud, Vikrant Yadav, Chun Yik Wong

ACS Sustainable Chemistry & Engineering　12　(45)　16518-16523　2024/11/01
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acssuschemeng.4c05143 　

ISSN： 2168-0485

eISSN： 2168-0485
An ionic liquid containing arsonium cation Peer-reviewed

Ryoto Inaba, Tomohiro Imai, Showa Kitajima, Hitoshi Kasai, Kouki Oka, Ryoyu Hifumi, Ikuyoshi Tomita, Masahiro Yoshizawa-Fujita, Kensuke Naka, Hiroaki Imoto

Chemical Communications　2024/10
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d4cc05072j 　

ISSN： 1359-7345

eISSN： 1364-548X

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Cations in ionic liquids (ILs) are typically derived from ammonium or phosphonium structures with long alkyl chains, and it is well established that the central atom significantly influences the properties...
Photodynamic antimicrobial activity of polydiacetylene crystal nanostructure against E. coli Peer-reviewed

Mohammad Oves, Ryuju Suzuki, Hirotaka Nakatsuji, Yoshitaka Koseki, Sanjay Kumar, Kouki Oka, Hitoshi Kasai

MRS Communications　2024/08/08
Publisher: Springer Science and Business Media LLC
DOI： 10.1557/s43579-024-00622-8 　

eISSN： 2159-6867
Highly Fluorinated Nanospace in Porous Organic Salts with High Water Stability/Capability and Proton Conductivity Peer-reviewed

Takahiro Ami, Showa Kitajima, Kouki Oka, Norimitsu Tohnai

Angewandte Chemie　2024/06/20
Publisher: Wiley
DOI： 10.1002/ange.202407484 　

ISSN： 0044-8249

eISSN： 1521-3757

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Water in hydrophobic nanospaces shows specific dynamic properties different from bulk water. The investigation of these properties is important in various research fields, including materials science, chemistry, and biology. The elucidation of the correlation between properties of water and hydrophobic nanospaces requires nanospaces covered only with simple hydrophobic group (e.g., fluorine) without impurities such as metals. This work successfully fabricated all‐organic diamondoid porous organic salts (d‐POSs) with highly fluorinated nanospaces, wherein hydrophobic fluorine atoms are densely exposed on the void surfaces, by combining fluorine substituted triphenylmethylamine (TPMA) derivatives with tetrahedral tetrasulfonic acid. This d‐POSs with a highly fluorinated nanospace significantly improved their water stability, retaining their crystal structure even when immersed in water over one week. Moreover, this highly hydrophobic and fluorinated nanospace adsorbs 160 mL(STP)/g of water vapor at Pe/P0 = 0.90; this is the first hydrophobic nanospace, which water molecules can enter, in an all‐organic porous material. Furthermore, this highly fluorinated nanospace exhibits very high proton conductivity (1.34 × 10−2 S/cm) at 90°C and 95%RH. POSs with tailorable nanospaces may significantly advance the elucidation of the properties of specific “water” in pure hydrophobic environments.
Unlocking the Charge‐storage Potential of a Phenanthraquinone‐based Two‐dimensional Covalent Organic Framework (2D COF) Peer-reviewed

Tyran Günther, Daniel Hedbom, Michelle Åhlén, Haruka Yoshino, Hitoshi Miyasaka, Hitoshi Kasai, Kouki Oka, Rikard Emanuelsson

ChemPlusChem　2024/06/04
Publisher: Wiley
DOI： 10.1002/cplu.202400184 　

ISSN： 2192-6506

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The high surface area, open pore‐structure and atomic‐level organization inherent in many covalent organic frameworks (COFs) make them an attractive polymer platform for developing functional materials. Herein, a chemically robust 2D COF (TpOMe‐DAPQ COF) containing phenanthraquinone moieties was prepared by condensing 2,4,6‐trimethoxy‐1,3,5‐benzenetricarbaldehyde (TpOMe) and 2,7‐diamino‐9,10‐phenanthraquinone (DAPQ) using the convenient mechanochemical method. The poor charge‐storage capacity of the pristine TpOMe‐DAPQ COF was substantially improved by first investigating its redox‐site accessibility (RSA) using different conductivity‐enhancement methods, and then optimizing the amount of EDOT needed to perform an in‐situ polymerization. The resulting composite (0.4EDOT@TpOMe‐DAPQ) was characterized and its enhanced charge‐storage capabilities enabled it to be used as an anode material in an aqueous Mn beaker‐cell battery capable of delivering 0.76 V. This work outlines the rational design approach used to develop a functional charge‐storage material utilizing a COF‐based polymerization platform.
Redox‐active organic molecules supported by polyhedral oligomeric silsesquioxane Peer-reviewed

Ryota Tanaka, Showa Kitajima, Norimitsu Tohnai, Kouki Oka, Hiroaki Imoto, Kensuke Naka

ChemNanoMat　2024/03/27
Publisher: Wiley
DOI： 10.1002/cnma.202400122 　

ISSN： 2199-692X

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Organic redox molecules have attracted considerable attention because of their abundant availability and excellent design flexibility. For practical applications, these molecules must be anchored onto scaffolds such as polymers to prevent crystallization and elution into the electrolyte. In this study, we explore the use of polyhedral oligomeric silsesquioxane (POSS) derivatives as scaffolds for anthraquinone (AQ) and hydroquinone. We investigated the cage structure of POSS and the number of redox units incorporated. Notably, a corner‐opened POSS (CO‐POSS) variant with three AQ units exhibited reversible redox behavior under neutral, acidic, and basic conditions. Furthermore, we examined the air‐battery performance of AQ‐modified CO‐POSS as an anode‐active material.
Spirobifluorene‐Based Porous Organic Salts: Their Porous Network Diversification and Construction of Chiral Helical Luminescent Structures Peer-reviewed

Kohei Okubo, Kouki Oka, Keiho Tsuchiya, Atsunori Tomimoto, Norimitsu Tohnai

Angewandte Chemie　2024/02/16
Publisher: Wiley
DOI： 10.1002/ange.202400475 　

ISSN： 0044-8249

eISSN： 1521-3757

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Abstract Porous organic salts (POSs) are organic porous materials assembled via charge‐assisted hydrogen bonds between strong acids and bases such as sulfonic acids and amines. To diversify the network topology of POSs and extend its functions, this study focused on using 4,4′,4′′,4′′′‐(9,9′‐spirobi[fluorene]‐2,2′,7,7′‐tetrayl)tetrabenzenesulfonic acid (spiroBPS), which is a tetrasulfonic acid comprising a square planar skeleton. The POS consisting of spiroBPS and triphenylmethylamine (TPMA) (spiroBPS/TPMA) was constructed from the two‐fold interpenetration of an orthogonal network with pts topology, which has not been reported in conventional POSs, owing to the shape of the spirobifluorene backbone. Furthermore, combining tris(4‐chlorophenyl)methylamine (TPMA‐Cl) and tris(4‐bromophenyl)methylamine (TPMA‐Br), which are bulkier than TPMA owing to the introduction of halogens at the p‐position of the phenyl groups with spiroBPS allows us to construct novel POSs (spiroBPS/TPMA‐Cl and spiroBPS/TPMA‐Br). These POSs were constructed from a chiral helical network with pth topology, which was induced by the steric hindrance between the halogens and the curved fluorene skeleton. Moreover, spiroBPS/TPMA‐Cl with pth topology exhibited circularly polarized luminescence (CPL) in the solid state, which has not been reported in hydrogen‐bonded organic frameworks (HOFs).
Breathing Metal–Organic Frameworks Supported by an Arsenic-Bridged 4,4′-Bipyridine Ligand Peer-reviewed

Kazuma Kikuchi, Hiroi Sei, Kohei Okubo, Norimitsu Tohnai, Kouki Oka, Shun Dekura, Takashi Kikuchi, Hiroaki Imoto, Kensuke Naka

Inorganic Chemistry　2024/02/16
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.inorgchem.3c04570 　

ISSN： 0020-1669

eISSN： 1520-510X
Incorporation of deuterated coronene into cage-like sodalite-type porous organic salts and improvement of room-temperature phosphorescence properties Peer-reviewed

Hiroi Sei, Kouki Oka, Tomoki Furuta, Norimitsu Tohnai

Bulletin of the Chemical Society of Japan　97　(2)　2024/02/10
Publisher: Oxford University Press (OUP)
DOI： 10.1093/bulcsj/uoad023 　

ISSN： 0009-2673

eISSN： 1348-0634

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Abstract Host materials with external heavy atom effects do not change the chemical structures of incorporated luminescent molecules but promote intersystem crossing from the excited singlet state to the excited triplet state, which induces room-temperature phosphorescence (RTP). The deuteration of luminescent molecules suppresses non-radiative deactivation via C–H stretching vibration; therefore, the improvement of both phosphorescence lifetime and quantum efficiency (i.e. isotope effect) is expected. Although a combination of the external heavy atom effect and isotope effect could be expected to improve phosphorescent performances dramatically, an environment with a strong external heavy atom effect (density of iodine atoms ≥0.65 gcm−3) increases non-radiative deactivation via spin-orbit coupling; therefore, the isotope effect is hindered, and the phosphorescent lifetime and quantum efficiency are not usually improved. In the current work, we constructed cage-like sodalite-type porous organic salts (s-POSs) where the density of iodine atoms (0.55 gcm−3) was moderate (0.13 ̶ 0.65 gcm−3). Incorporation of a deuterated representative luminescent molecule such as coronene (coronene-d12) into s-POSs enabled the exerting of both the external heavy atom effect and isotope effect, which successfully improved both RTP lifetime (1.1 times) and quantum efficiency (1.6 times) over those of an incorporated ordinary coronene (coronene-h12).
Construction of Triptycene Molecular Rotors with Intermeshing Arrangement and Low Rotational Barrier Peer-reviewed

Tomoki Furuta, Kouki Oka, Norimitsu Tohnai

Bulletin of the Chemical Society of Japan　2024/02/08
Publisher: Oxford University Press (OUP)
DOI： 10.1093/bulcsj/uoae013 　

ISSN： 0009-2673

eISSN： 1348-0634

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Abstract Molecular rotors are one of the building blocks of molecular machines and are nano-sized machines with mechanically rotating moieties. Among them, intermeshing triptycenes with a gear-like skeleton allows the construction of a molecular rotor that transmits rotational motion. For triptycenes to mesh with each other without loss of rotation, intermeshing them in parallel and adjusting the distance between their axis to 8.1 Å are required. However, with conventional methods, because of the restrictions on bond lengths and atomic radius, achieving an ideal arrangement in which the triptycenes mesh in parallel at 8.1 Å has been difficult. In this work, we synthesized disulfonic acid containing a triptycene as a rotator, and combining it with amines of two different steric factors (normal-amylamine (nAmA) and guanidine (Gu)) allowed us to prepare organic salts with varying arrangements of triptycene. In the organic salt with the planar amine (Gu), the crystal structure was close to the ideal intermeshing arrangement of triptycene, and the distance between their axis was 7.7 Å. The T1ρ 13C spin-lattice relaxation time by solid-state NMR demonstrated that triptycene rotates efficiently at 24 kHz at 313 K with a low rotational barrier (10.9 kcal/mol) compared to non-intermeshing structures.
An Expanded Hydrogen-bonded Organic Framework Formed by A Tetrakis(terphenyl)ethene Derivative Peer-reviewed

Mao Yamaguchi, Mario de la Hoz Tomás, Ayano Fujiwara, Ryusei Oketani, Kohei Okubo, Kouki Oka, Norimitsu Tohnai, Abderrazzak Douhal, Ichiro Hisaki

Bulletin of the Chemical Society of Japan　2024/01/23
Publisher: Oxford University Press (OUP)
DOI： 10.1093/bulcsj/uoae004 　

ISSN： 0009-2673

eISSN： 1348-0634

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Abstract A low-density hydrogen-bonded organic framework (HOF) with channel aperture with dimension of 33.8 Å × 55.2 Å was constructed from a tetrakis(terphenyl)ethene derivative. The structure was successfully characterized by single crystalline X-ray diffraction analysis. Although solvent molecules are included in the channel, the present framework is one of the HOFs with the largest aperture. The framework is based on H-bonded sql-network that stacks in eclipse fashion. The interlayer interactions were thoroughly investigated on the basis of the crystal structure. Interestingly, tetraarylethene-based three analogous tetracarboxylic acids including the title compounds formed the same H-bonded sql-network as a lower-dimensional supramolecular motif, while the motifs are assembled in completely different ways to give the corresponding three types of the framework, indicating the importance of precise design of the secondary interactions between the lower dimensional motifs. In solid state, the molecular unit of the constructed HOF shows a largely Stokes shifted and strong emission due to a fast (&lt; 15 ps) ICT and a relatively slower (90 ps) intermolecular PT reaction, while in DMF is exhibits a strong H-bond with the solvent.
Ice-Like Dynamics of Water Clusters Peer-reviewed

Kouki Oka, Hiroshi Akiba, Norimitsu Tohnai, Toshimichi Shibue, Osamu Yamamuro

The Journal of Physical Chemistry Letters　15　(1)　267-271　2024/01/02
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.3c02754 　

ISSN： 1948-7185

eISSN： 1948-7185
Anticancer nano-prodrugs with drug release triggered by intracellular dissolution and hydrogen peroxide response

Aki Shibata, Yoshitaka Koseki, Keita Tanita, Showa Kitajima, Kouki Oka, Kiyotaka Maruoka, Ryuju Suzuki, Anh Thi Ngoc Dao, Hitoshi Kasai

Chemical Communications　60　(50)　6427-6430　2024
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d4cc02252a 　

ISSN： 1359-7345

eISSN： 1364-548X

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We developed prodrug nanoparticles that release drugs through intracellular dissolution and a cancer-specific hydrogen peroxide response.
Network Topology Diversification of Porous Organic Salts Peer-reviewed

Hiroi Sei, Kouki Oka, Yuta Hori, Yasuteru Shigeta, Norimitsu Tohnai

Chemical Science　2024
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d4sc01218f 　

ISSN： 2041-6520

eISSN： 2041-6539

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Hydrogen-bonded organic frameworks (HOFs) are porous organic materials constructed via hydrogen bonds. HOFs have solubility for specific high-polar organic solvents, and return to their components, which indicates their high recyclability....
Cation Recognition by Dibenzoarsacrowns

Kenta Ogawa, Akifumi Sumida, Takahiro Ami, Kouki Oka, Norimitsu Tohnai, Yusuke Miyake, Hiroaki Imoto, Kensuke Naka

Asian Journal of Organic Chemistry　2023/11/06
Publisher: Wiley
DOI： 10.1002/ajoc.202300525 　

ISSN： 2193-5807

eISSN： 2193-5815

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We recently reported dibenzoarsacrowns as a novel class of host molecules, and in this work, prepared four dibenzoarsacrowns:12‐dibenzoarsacrown‐4, 15‐dibenzoarsacrown‐5, 18‐dibenzoarsacrown‐6, and 21‐dibenzoarsacrown‐7, and investigated their guest recognition behaviors for alkali metal and ammonium cations (Li+, Na+, K+, and NH4+). It was found that the triphenylarsine moiety of the dibenzoarsacrowns could be electrochemically oxidized and that their oxidation potentials shifted in response to perturbation because of the weak interaction between the arsenic atom and guest cations. Thus, dibenzoarsacrowns could electrochemically detect cations with sizes that fit the host cavity. Electron spin resonance measurements revealed the generation of cation radical species of arsenic under the application of voltage and supported the idea that the interaction between the arsenic atom and guest cations played a crucial role in the detection of cations. In addition, ion chromatography studies showed that size‐selective cation recognition by dibenzoarsacrowns was achievable even in aqueous solutions.
Control of Relative Positions of Electron‐Donor and Electron‐Acceptor Molecules in Charge‐Transfer Complexes for Luminescent Property Modulation

Yo Kinoshita, Kouki Oka, Hiromi Nakajima, Norimitsu Tohnai

Chemistry – A European Journal　2023/10/24
Publisher: Wiley
DOI： 10.1002/chem.202302965 　

ISSN： 0947-6539

eISSN： 1521-3765

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Charge‐transfer complexes can exhibit various physical properties, which depend on the relative positions of electron‐donor and electron‐acceptor molecules. Several studies have investigated the relationship between the relative positions of electron‐donor and electron‐acceptor molecules and their luminescence properties. However, elucidating the pure correlation between the relative positions and detailed luminescence processes without changing their molecular structures has been unexplored. Herein, we report the relative‐position‐control based on charge‐assisted hydrogen bonds between sulfo and amino groups and on alkylamines’ steric factors, and report concomitant luminescent property modulation. From anthracene‐2,6‐disulfonic acid and 1,2,4,5‐tetracyanobenzene as electron‐donor and electron‐acceptor molecules, and various alkylamines, six charge‐transfer complexes were prepared. Different alkylamines' steric factors drastically and precisely changed the relative positions of the electron‐donor and electron‐acceptor molecules without changing their molecular structures. Consequently, the six crystals exhibited maximum emission wavelengths from 543 to 624 nm and different luminescence processes.
Inside front cover Peer-reviewed

Journal of Materials Chemistry A　11　(26)　13798-13798　2023/07
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d3ta90135a 　

ISSN： 2050-7488

eISSN： 2050-7496
Redox-site accessibility of composites containing a 2D redox-active covalent organic framework: from optimization to application Peer-reviewed

Tyran Günther, Kouki Oka, Sandra Olsson, Michelle Åhlén, Norimitsu Tohnai, Rikard Emanuelsson

Journal of Materials Chemistry A　11　(26)　13923-13931　2023/07
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d3ta00422h 　

ISSN： 2050-7488

eISSN： 2050-7496

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A systematic method is presented which demonstrates how accessing more redox-active sites in a poorly conducting 2D COF can be done in a rational manner. An optimised and dramatically improved charge-storage composite was produced using this method.
Porous Organic Salts Composed of Terphenyl Sulfonic Acid and Their Bottleneck Designability Peer-reviewed

Ryota Akai, Kouki Oka, Naoki Okada, Takahiro Ami, Norimitsu Tohnai

European Journal of Organic Chemistry　2023/06/12
Publisher: Wiley
DOI： 10.1002/ejoc.202300417 　

ISSN： 1434-193X

eISSN： 1099-0690
Incorporation of Coronene into Cage‐like Porous Organic Salts and Induction of its Room‐Temperature Phosphorescence in Air Peer-reviewed

Hiroi Sei, Kouki Oka, Norimitsu Tohnai

ChemNanoMat　2023/06/06
Publisher: Wiley
DOI： 10.1002/cnma.202300248 　

ISSN： 2199-692X

eISSN： 2199-692X
All‐Solid‐State Rechargeable Air Batteries Using Dihydroxybenzoquinone and Its Polymer as the Negative Electrode Peer-reviewed

Makoto Yonenaga, Yusuke Kaiwa, Kouki Oka, Kenichi Oyaizu, Kenji Miyatake

Angewandte Chemie International Edition　2023/06/02
Publisher: Wiley
DOI： 10.1002/anie.202307351 　

ISSN： 1433-7851

eISSN： 1521-3773
Accelerated Oxidative Degradation of Phosphonium-Type Ionic Liquid with <scp>l</scp>-Prolinate Anion: Degradation Mechanism and CO₂ Separation Performance Peer-reviewed

Hiroi Sei, Yu Nagai Kanasaki, Kouki Oka, Norimitsu Tohnai, Yuki Kohno, Takashi Makino

ACS Omega　2023/05/31
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acsomega.3c02116 　

ISSN： 2470-1343

eISSN： 2470-1343
All‐Solid‐State Rechargeable Air Batteries Using Dihydroxybenzoquinone and Its Polymer as the Negative Electrode Peer-reviewed

Makoto Yonenaga, Yusuke Kaiwa, Kouki Oka, Kenichi Oyaizu, Kenji Miyatake

Angewandte Chemie　2023/05/02
Publisher: Wiley
DOI： 10.1002/ange.202304366 　

ISSN： 0044-8249

eISSN： 1521-3757
All‐Solid‐State Rechargeable Air Batteries Using Dihydroxybenzoquinone and Its Polymer as the Negative Electrode Peer-reviewed

Makoto Yonenaga, Yusuke Kaiwa, Kouki Oka, Kenichi Oyaizu, Kenji Miyatake

Angewandte Chemie International Edition　2023/05/02
Publisher: Wiley
DOI： 10.1002/anie.202304366 　

ISSN： 1433-7851

eISSN： 1521-3773
Precise Control of the Molecular Arrangement of Organic Semiconductors for High Charge Carrier Mobility Peer-reviewed

Ryota Akai, Kouki Oka, Shun Dekura, Kazuyoshi Yoshimi, Hatsumi Mori, Ryosuke Nishikubo, Akinori Saeki, Norimitsu Tohnai

The Journal of Physical Chemistry Letters　3461-3467　2023/04/03
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.3c00334 　

ISSN： 1948-7185

eISSN： 1948-7185
Cage‐Like Sodalite‐Type Porous Organic Salts Enabling Luminescent Molecule's Incorporation and Room‐temperature Phosphorescence Induction in Air Peer-reviewed

Hiroi Sei, Kouki Oka, Hikaru Sotome, Hiroshi Miyasaka, Norimitsu Tohnai

Small　2023/03/26
Publisher: Wiley
DOI： 10.1002/smll.202301887 　

ISSN： 1613-6810

eISSN： 1613-6829
3,11‐Diaminodibenzo[ a,j ]phenazine: Synthesis, Properties, and Applications to Tröger's Base‐Forming Ladder Polymerization Peer-reviewed

Saika Izumi, Keiki Inoue, Yuya Nitta, Tomoya Enjou, Takahiro Ami, Kouki Oka, Norimitsu Tohnai, Satoshi Minakata, Takanori Fukushima, Fumitaka Ishiwari, Youhei Takeda

Chemistry – A European Journal　29　(14)　2023/02/08
Publisher: Wiley
DOI： 10.1002/chem.202202702 　

ISSN： 0947-6539

eISSN： 1521-3765
Design of a Robust and Strong-Acid MOF Platform for the Selective Ammonium Recovery and Proton Conductivity Peer-reviewed

Teppei Yamada, Genki Hatakeyama, Hongyao Zhou, Takashi Kikuchi, Masaki Nishio, Kouki Oka, Masaaki Sadakiyo, Yusuke Nishiyama

Chemical Science　2023
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d3sc02743k 　

ISSN： 2041-6520

eISSN： 2041-6539

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Metal–organic frameworks (MOFs) are potential candidates for the platform of the solid acid; however, no MOF has been reported, which has both aqueous ammonium stability and a strong acid site....
Statically and Dynamically Flexible Hydrogen-bonded Frameworks Based on 4,5,9,10-Tetrakis(4-carboxyphenyl)pyrene Peer-reviewed

Taito Hashimoto, Ryusei Oketani, Asato Inoue, Kohei Okubo, Kouki Oka, Norimitsu Tonai, Kazuhide Kamiya, Shuji Nakanishi, Ichiro Hisaki

Chemical Communications　2023
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d3cc01877f 　

ISSN： 1359-7345

eISSN： 1364-548X

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In this communication, we described static and dynamic flexibility of a HOF composed of tetratopic carboxylic acid CP-Py. Void spaces of the framework can be statically modulated upon including different...
Accelerating the dehydrogenation reaction of alcohols by introducing them into poly(allylamine)

Kouki Oka, Yusuke Kaiwa, Kazuki Kobayashi, Yuka Tobita, Kenichi Oyaizu

Polymer Chemistry　14　(21)　2588-2591　2023
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d3py00404j 　

ISSN： 1759-9954

eISSN： 1759-9962

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This paper demonstrated accelerating the dehydrogenation reaction of alcohols by introducing them into poly(allylamine). Contrary to popular belief, the reaction rate was higher by one order of magnitude compared to that in single molecules.
The Introduction of a Base Component to Porous Organic Salts and Their CO2 Storage Capability Peer-reviewed

Takahiro Ami, Kouki Oka, Keiho Tuchiya, Wataru Kosaka, Hitoshi Miyasaka, Norimitsu Tohnai

CrystEngComm　25　(15)　2321-2325　2023
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d3ce00086a 　

eISSN： 1466-8033

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Porous organic salts (POSs) are constructed by charge-assisted hydrogen bonding between amino and sulfonic groups, and can design a variety of porous structures based on the molecular design. In particular,...
Molecular Arrangement Control of [1]Benzothieno[3,2-b][1]benzothiophene (BTBT) via Charge-Assisted Hydrogen Bond Peer-reviewed

Ryota Akai, Kouki Oka, Shun Dekura, Hatsumi Mori, Norimitsu Tohnai

Bulletin of the Chemical Society of Japan　2022/06/15
Publisher: The Chemical Society of Japan
DOI： 10.1246/bcsj.20220134 　

ISSN： 0009-2673

eISSN： 1348-0634
Systematic Arrangement Control of Functional Organic Molecules Peer-reviewed

Ryota Akai, Kouki Oka, Ryunosuke Nishida, Norimitsu Tohnai

CrystEngComm　24　(23)　4180-4186　2022/05/09
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d2ce00336h 　

eISSN： 1466-8033

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Functional organic molecules, especially π-conjugated molecules, have tunable functions according to their molecular design. Since their properties are significantly affected by the overlap of π-orbitals between adjacent molecules as well...
Controlling the Movability and Excimer Formation of Functional Organic Molecules Peer-reviewed

Ryota Akai, Kouki Oka, Ryunosuke Nishida, Norimitsu Tohnai

Bulletin of the Chemical Society of Japan　95　(7)　1111-1116　2022/05/07
Publisher: The Chemical Society of Japan
DOI： 10.1246/bcsj.20220107 　

ISSN： 0009-2673

eISSN： 1348-0634
Systematic Study of Pnictogen-Fused Heterofluorenes Peer-reviewed

Ryoto Inaba, Kouki Oka, Takahiro Iwami, Yusuke Miyake, Kunihiko Tajima, Hiroaki Imoto, Kensuke Naka

Inorganic Chemistry　61　(19)　7318-7326　2022/05/06
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.inorgchem.2c00158 　

ISSN： 0020-1669

eISSN： 1520-510X
Porous Organic Salts: Diversifying Void Structures and Environments Peer-reviewed

Takahiro Ami, Kouki Oka, Keiho Tsuchiya, Norimitsu Tohnai

Angewandte Chemie　2022/05/03
Publisher: Wiley
DOI： 10.1002/ange.202202597 　

ISSN： 0044-8249

eISSN： 1521-3757
Poly(vinyl diphenylquinoxaline) as a hydrogen storage material toward rapid hydrogen evolution Peer-reviewed

Kouki Oka, Miho Kataoka, Hiroyuki Nishide, Kenichi Oyaizu

MRS Communications　12　(2)　213-216　2022/04
Publisher: Springer Science and Business Media LLC
DOI： 10.1557/s43579-022-00164-x 　

ISSN： 2159-6859

eISSN： 2159-6867
Cover Image

Kouki Oka, Yuka Tobita, Miho Kataoka, Kazuki Kobayashi, Yusuke Kaiwa, Hiroyuki Nishide, Kenichi Oyaizu

Polymer International　71　(3)　2022/03
Publisher: Wiley
DOI： 10.1002/pi.6379 　

ISSN： 0959-8103

eISSN： 1097-0126
Polymers for Safe Hydrogen Storage Peer-reviewed

Kouki Oka, Yuka Tobita, Miho Kataoka, Kazuki Kobayashi, Yusuke Kaiwa, Hiroyuki Nishide, Kenichi Oyaizu

Polymer International　71　(3)　2022/03
Publisher: Wiley
DOI： 10.1002/pi.6379 　

ISSN： 0959-8103

eISSN： 1097-0126
Hydrophilic isopropanol/acetone‐substituted polymers for safe hydrogen storage Peer-reviewed

Kouki Oka, Yuka Tobita, Miho Kataoka, Kazuki Kobayashi, Yusuke Kaiwa, Hiroyuki Nishide, Kenichi Oyaizu

Polymer International　71　(3)　348-351　2022/03
Publisher: Wiley
DOI： 10.1002/pi.6337 　

ISSN： 0959-8103

eISSN： 1097-0126
Tetrachlorocatecholates of triarylarsines as a novel class of Lewis acids Peer-reviewed

Akane Chishiro, Ippei Akioka, Akifumi Sumida, Kouki Oka, Norimitsu Tohnai, Takashi Yumura, Hiroaki Imoto, Kensuke Naka

Dalton Transactions　51　(36)　13716-13724　2022
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d2dt02145e 　

ISSN： 1477-9226

eISSN： 1477-9234

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Tetrachlorocatecholates of triarylarsines have been synthesized as a novel class of pnictogen-mediated Lewis acids. Their Lewis acidities and electronic properties were studied in comparison with the phosphorus and antimony analogues.
Poly(3‐alkylthiophene) Films as Solvent‐Processable Photoelectrocatalysts for Efficient Oxygen Reduction to Hydrogen Peroxide Peer-reviewed

Kouki Oka, Koichiro Kamimori, Bjorn Winther-Jensen, Hiroyuki Nishide

Advanced Energy and Sustainability Research　2　(12)　2100103-2100103　2021/12
Publisher: Wiley
DOI： 10.1002/aesr.202100103 　

ISSN： 2699-9412

eISSN： 2699-9412
Alcohol-Substituted Vinyl Polymers for Stockpiling Hydrogen Peer-reviewed

Kouki Oka, Miho Kataoka, Yusuke Kaiwa, Kenichi Oyaizu

Bulletin of the Chemical Society of Japan　94　(11)　2770-2773　2021/11/15
Publisher: The Chemical Society of Japan
DOI： 10.1246/bcsj.20210283 　

ISSN： 0009-2673

eISSN： 1348-0634
Synthesis of vinyl polymers substituted with 2-propanol and acetone and investigation of their reversible hydrogen storage capabilities Peer-reviewed

Kouki Oka, Yuka Tobita, Miho Kataoka, Saki Murao, Kazuki Kobayashi, Shuhei Furukawa, Hiroyuki Nishide, Kenichi Oyaizu

Polymer Journal　53　(7)　799-804　2021/07
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41428-021-00475-1 　

ISSN： 0032-3896

eISSN： 1349-0540
Two States of Water Converge to One State below 215 K Peer-reviewed

Kouki Oka, Toshimichi Shibue, Natsuhiko Sugimura, Yuki Watabe, Midori Tanaka, Bjorn Winther-Jensen, Hiroyuki Nishide

The Journal of Physical Chemistry Letters　12　(24)　5802-5806　2021/06/24
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.1c01132 　

ISSN： 1948-7185

eISSN： 1948-7185
Hydrophilic Anthraquinone-Substituted Polymer: Its Environmentally Friendly Preparation and Efficient Charge/Proton-Storage Capability for Polymer–Air Secondary Batteries Peer-reviewed

Kouki Oka, Saki Murao, Miho Kataoka, Hiroyuki Nishide, Kenichi Oyaizu

Macromolecules　54　(10)　4854-4859　2021/05/25
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.macromol.1c00865 　

ISSN： 0024-9297

eISSN： 1520-5835
H ₂ O ₂ Production: Copolymer of Phenylene and Thiophene toward a Visible‐Light‐Driven Photocatalytic Oxygen Reduction to Hydrogen Peroxide (Adv. Sci. 5/2021) Peer-reviewed

Kouki Oka, Hiroyuki Nishide, Bjorn Winther‐Jensen

Advanced Science　8　(5)　2170023-2170023　2021/03
Publisher: Wiley
DOI： 10.1002/advs.202170023 　

ISSN： 2198-3844

eISSN： 2198-3844
Facile reversible hydrogenation of a poly(6‐vinyl‐2,3‐dimethyl‐1,2,3,4‐tetrahydroquinoxaline) gel‐like solid Peer-reviewed

Yusuke Kaiwa, Kouki Oka, Hiroyuki Nishide, Kenichi Oyaizu

Polymers for Advanced Technologies　32　(3)　1162-1167　2021/03
Publisher: Wiley
DOI： 10.1002/pat.5163 　

ISSN： 1042-7147

eISSN： 1099-1581
Copolymer of Phenylene and Thiophene toward a Visible‐Light‐Driven Photocatalytic Oxygen Reduction to Hydrogen Peroxide Peer-reviewed

Kouki Oka, Hiroyuki Nishide, Bjorn Winther‐Jensen

Advanced Science　8　(5)　2003077-2003077　2021/03
Publisher: Wiley
DOI： 10.1002/advs.202003077 　

ISSN： 2198-3844

eISSN： 2198-3844
An Alternative to Carbon Additives: The Fabrication of Conductive Layers Enabled by Soluble Conducting Polymer Precursors – A Case Study for Organic Batteries Peer-reviewed

Christian Strietzel, Kouki Oka, Maria Strømme, Rikard Emanuelsson, Martin Sjödin

ACS Applied Materials & Interfaces　13　(4)　5349-5356　2021/02/03
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acsami.0c22578 　

ISSN： 1944-8244

eISSN： 1944-8252
Nonpolar Water Clusters: Proton Nuclear Magnetic Resonance Spectroscopic Evidence for Transformation from Polar Water to Nonpolar Water Clusters in Liquid State Peer-reviewed

Kouki Oka, Toshimichi Shibue, Natsuhiko Sugimura, Yuki Watabe, Bjorn Winther-Jensen, Hiroyuki Nishide

The Journal of Physical Chemistry Letters　12　(1)　276-279　2021/01/14
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.0c02646 　

ISSN： 1948-7185

eISSN： 1948-7185
Completely Solar-Driven Photoelectrochemical Water Splitting Using a Neat Polythiophene Film Peer-reviewed

Kouki Oka, Hiroyuki Nishide, Bjorn Winther-Jensen

Cell Reports Physical Science　2　(1)　100306-100306　2021/01
Publisher: Elsevier BV
DOI： 10.1016/j.xcrp.2020.100306 　

ISSN： 2666-3864

eISSN： 2666-3864
Charge- and Proton-Storage Capability of Naphthoquinone-Substituted Poly(allylamine) as Electrode-Active Material for Polymer–Air Secondary Batteries Peer-reviewed

Kouki Oka, Saki Murao, Kazuki Kobayashi, Hiroyuki Nishide, Kenichi Oyaizu

ACS Applied Energy Materials　3　(12)　12019-12024　2020/12/28
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acsaem.0c02178 　

ISSN： 2574-0962

eISSN： 2574-0962
Rechargeable proton exchange membrane fuel cell containing an intrinsic hydrogen storage polymer Peer-reviewed

Junpei Miyake, Yasunari Ogawa, Toshiki Tanaka, Jinju Ahn, Kouki Oka, Kenichi Oyaizu, Kenji Miyatake

Communications Chemistry　3　(1)　2020/12
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s42004-020-00384-z 　

eISSN： 2399-3669
A Polymer Sheet‐Based Hydrogen Carrier Peer-reviewed

Kouki Oka, Yusuke Kaiwa, Miho Kataoka, Ken‐ichi Fujita, Kenichi Oyaizu

European Journal of Organic Chemistry　2020　(36)　5876-5879　2020/09/30
Publisher: Wiley
DOI： 10.1002/ejoc.202001004 　

ISSN： 1434-193X

eISSN： 1099-0690
Conducting Redox Polymer as Organic Anode Material for Polymer‐Manganese Secondary Batteries Peer-reviewed

Kouki Oka, Rebecka Löfgren, Rikard Emanuelsson, Hiroyuki Nishide, Kenichi Oyaizu, Maria Strømme, Martin Sjödin

ChemElectroChem　7　(15)　3336-3340　2020/08/03
Publisher: Wiley
DOI： 10.1002/celc.202000711 　

ISSN： 2196-0216

eISSN： 2196-0216
Reversible Hydrogen Fixation and Release under Mild Conditions by Poly(vinylquinoxaline) Peer-reviewed

Kouki Oka, Yusuke Kaiwa, Shuhei Furukawa, Hiroyuki Nishide, Kenichi Oyaizu

ACS Applied Polymer Materials　2　(7)　2756-2760　2020/07/10
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acsapm.0c00338 　

ISSN： 2637-6105

eISSN： 2637-6105
Conducting Redox Polymer as a Robust Organic Electrode‐Active Material in Acidic Aqueous Electrolyte towards Polymer–Air Secondary Batteries Peer-reviewed

Kouki Oka, Christian Strietzel, Rikard Emanuelsson, Hiroyuki Nishide, Kenichi Oyaizu, Maria Strømme, Martin Sjödin

ChemSusChem　13　(9)　2280-2285　2020/05/08
Publisher: Wiley
DOI： 10.1002/cssc.202000627 　

ISSN： 1864-5631

eISSN： 1864-564X
Supercooled Low-Entropy Water Clusters Peer-reviewed

Kouki Oka, Toshimichi Shibue, Natsuhiko Sugimura, Yuki Watabe, Bjorn Winther-Jensen, Hiroyuki Nishide

The Journal of Physical Chemistry Letters　11　(9)　3667-3671　2020/05/07
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.0c00631 　

ISSN： 1948-7185

eISSN： 1948-7185
Poly(dihydroxybenzoquinone): Its high-density and robust charge storage capability in rechargeable acidic polymer-air batteries Peer-reviewed

Kouki Oka, Shuhei Furukawa, Saki Murao, Tatsuya Oka, Hiroyuki Nishide, Kenichi Oyaizu

Chemical Communications　56　(29)　4055-4058　2020/04

DOI： 10.1039/d0cc00660b 　

ISSN： 1359-7345

eISSN： 1364-548X
Chapter 4. Radical Polymers for Rechargeable Batteries Peer-reviewed

Kouki Oka, Hiroyuki Nishide

Polymer Chemistry Series　137-165　2020
Publisher: Royal Society of Chemistry
DOI： 10.1039/9781788019743-00137 　

ISSN： 2044-0804
Long-lived water clusters in hydrophobic solvents investigated by standard NMR techniques Peer-reviewed

Kouki Oka, Toshimichi Shibue, Natsuhiko Sugimura, Yuki Watabe, Bjorn Winther-Jensen, Hiroyuki Nishide

Scientific Reports　9　(1)　2019/12
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41598-018-36787-1 　

eISSN： 2045-2322
Characterization of PEDOT-Quinone conducting redox polymers in water-in-salt electrolytes for safe and high-energy Li-ion batteries Peer-reviewed

Kouki Oka, Christian Strietzel, Rikard Emanuelsson, Hiroyuki Nishide, Kenichi Oyaizu, Maria Strømme, Martin Sjödin

Electrochemistry Communications　105　106489-106489　2019/08
Publisher: Elsevier BV
DOI： 10.1016/j.elecom.2019.106489 　

ISSN： 1388-2481
Reversible Hydrogen Releasing and Fixing with Poly(Vinylfluorenol) through a Mild Ir‐Catalyzed Dehydrogenation and Electrochemical Hydrogenation Peer-reviewed

Ryo Kato, Kouki Oka, Keisuke Yoshimasa, Masataka Nakajima, Hiroyuki Nishide, Kenichi Oyaizu

Macromolecular Rapid Communications　40　(16)　1900139-1900139　2019/08
Publisher: Wiley
DOI： 10.1002/marc.201900139 　

ISSN： 1022-1336

eISSN： 1521-3927
Water Splitting: Poly(1,4‐di(2‐thienyl))benzene Facilitating Complete Light‐Driven Water Splitting under Visible Light at High pH (Adv. Energy Mater. 6/2019)

Kouki Oka, Kanako Noguchi, Takeo Suga, Hiroyuki Nishide, Bjorn Winther‐Jensen

Advanced Energy Materials　9　(6)　1970017-1970017　2019/02
Publisher: Wiley
DOI： 10.1002/aenm.201970017 　

ISSN： 1614-6832

eISSN： 1614-6840
N-Phenyl naphthalene diimide pendant polymer as a charge storage material with high rate capability and cyclability Peer-reviewed

Subashani Maniam, Kouki Oka, Hiroyuki Nishide

MRS Communications　7　(4)　967-973　2017/12/01

DOI： 10.1557/mrc.2017.127 　

ISSN： 2159-6859

eISSN： 2159-6867

Show all ︎Show first 5

Misc. 1

Structures and physical properties of 2D Cu(II) coordination polymers with pyrazole-4-carboxylate ligands

堤咲良, 出倉駿, 出倉駿, 佐藤鉄, 佐藤鉄, 金城克樹, 佐藤卓, 北嶋奨羽, 岡弘樹, 岡弘樹, 笠井均, 笠井均, 芥川智行, 芥川智行

分子科学討論会講演プログラム&要旨(Web)　18th　2024

Books and Other Publications 4

持続可能な有機電池の創製

北嶋奨羽, 笠井均, 岡弘樹

技術情報協会月刊車載テクノロジー　2025/03
Batteries: The Future of Energy Storage

Ryota Akai, Norimitsu Tohnai, Kouki Oka

2024/08/16

ISBN: 9815129384
Redox Polymers for Energy and Nanomedicine

Kouki Oka, Hiroyuki Nishide

Royal Society of Chemistry　2020/10
有機結晶部会ニュースレター No.53 (電荷補助型水素結合に基づく分子配列制御による材料開発)

赤井亮太, 岡弘樹, 藤内謙光

公益社団法人日本化学会有機結晶部会　2023/01

Presentations 83

Novel Solid-State Organic Catalysts Towards Water-Splitting Invited

Kouki Oka

Applied Materials & Interfaces Conference (AMIC 2025)　2025/07/03
高純度なπ共役高分子薄膜の創製とその界面制御に関する研究 Invited

岡弘樹

2025年度第63回日本接着学会年次大会　2025/06/30
有機物から電池・触媒・エネルギーをつくる Invited

岡弘樹

日本技術士会統括本部化学部会講演会　2025/06/28
社会問題解決に貢献できる機能性有機材料の創製 Invited

岡弘樹

JACI 先端化学・材料技術部会新素材分科会/高選択性反応分科会現地分科会　2025/05/13
エネルギー製造・貯蔵・変換・活用を担う革新的な機能性有機材料の開発 Invited

岡弘樹

名古屋大学大学院工学研究科学術講演　2025/04/30
Development of Innovative Organic Energy Materials Invited

Kouki Oka

Innovative Materials for Sustainable Energy and Sensor 2025 (IMSE-2025)　2025/03/27
Development of New Organic Catalytic Material Invited

Kouki Oka

International Conference on Catalysis and Reaction Engineering 2025　2025/02/13
革新的な有機エネルギー材料の創製 Invited

岡弘樹

先端マテリアル研究交流講演会　2025/02/04
環境適合な有機ハイドライドの創出とグリーン水素の製造・貯蔵法の創製 Invited

岡弘樹

令和６年度新技術説明会　2025/01/16
Development of Innovative Organic Energy Materials (Plenary Lecture) Invited

Kouki Oka

Third International Conference on Science and Technology of Advanced Materials (STAM 25)　2025/01/09
革新的な有機エネルギー材料の開発 Invited

岡弘樹

東京農工大学中村・一川・田中研究室講演会　2025/01/06
環境適合な有機ハイドライドの創出とグリーン水素の製造・貯蔵法の構築 Invited

岡弘樹

青葉工学振興会賞等受賞者授賞式及び講演会　2024/12/13
有機固体研究者による溶液化学への挑戦 Invited

岡弘樹

第4回溶液化学研究会若手の会講演会　2024/12/09
リサイクル可能な革新的機能材料とデバイスの開発 Invited

岡弘樹

東北テックプラングランプリ2024　2024/11/23
機能性高分子の最前線 Invited

岡弘樹

山梨大学物理化学特別講義　2024/11/21
持続可能な社会実現に向けた革新的な有機エネルギー材料の開発 Invited

岡弘樹

令和６（2024）年度日本学術振興会育志賞受賞者交流会　2024/11/12
研究室紹介 Invited

岡弘樹

第４回マテリアル・計測ハイブリッド研究センター若手フォーラム　2024/11/06
Development of New Organic Functional Materials Invited

Kouki Oka

Thailand-Japan Symposium in Chemistry　2024/11/03
我が国の将来を担う機能性有機材料の開発 Invited

岡弘樹

『現代の生命科学』特別講義　2024/11/01
環境適合な有機ハイドライドの創出とグリーン水素の製造・貯蔵法の構築 Invited

岡弘樹

国民との対話 (早稲田高等学院)　2024/11/01
Development of Innovative Organic Energy Materials Invited

Kouki Oka

9TH JAPAN-THAI WORKSHOP ON THEORETICAL AND COMPUTATIONAL CHEMISTRY 2024　2024/10/11
Organic π-Conjugated Polymers as a Photoelectrocatalyst for Water-Splitting

Kouki Oka

2024/10/07
エネルギーの創・蓄・変・活を担う革新的な機能性有機材料の開発 Invited

岡弘樹

若手研究者研究交流会　2024/09/30
クリーンエネルギー製造を担う有機材料の開発 Invited

岡弘樹

先端化学・材料技術部会高選択性反応分科会講演会　2024/08/30
高分解能パルス冷中性子分光器による水クラスターのダイナミクスの解明 Invited

岡弘樹

第80回放射線科学研究会　2024/08/20
持続可能な社会実現に向けた有機エネルギー材料の開発 Invited

岡弘樹

技術士業務研究会7月例会講演　2024/07/12
Organic Energy Materials Towards a Sustainable Society Invited

Kouki Oka

The Second Symposium for Young Chemists: Innovation and Sustainability (SYNC 2024)　2024/06/24
技術シーズの産業化に向けて～大学発ベンチャーの立ち上げおよび企業内における研究事業化の支援に特化した取り組み～ Invited

岡弘樹

化学工学会第89年会　2024/03/19
地球温暖化の緩和に向けた高酸化耐性のCO2吸着剤の創製 Invited

岡弘樹

市村清新技術財団贈呈式　2024/02/13
Organic π-Conjugated Polymers as a Photoelectrocalyst towards Water-Splitting Invited

MRM2023/IUMRS-ICA2023　2023/12/14
革新的な”有機エネルギー材料”の創製 Invited

岡弘樹

上智大学理工学部物質生命理工学科コロキウム　2023/12/08
革新的な"有機エネルギー材料"の創製～反応から材料開発まで～ Invited

岡弘樹

横浜市立大学講演会　2023/12/07
Development of Organic Materials Towards Sustainable Energy Applications Invited

Carbon Chemistry Conferences 2023　2023/10/23
Development of Innovative Organic Energy Materials towards a Sustainable Society Invited

Kouki Oka

The 72nd Symposium on Macromolecules JAPAN-KOREA JOINT SESSION　2023/09/26
π共役高分子の革新的触媒能の開拓 Invited

岡弘樹

第132回触媒討論会「水素＋天然ガス＋燃料電池＋コンピュータ＋元素」研究会横断若手シンポジウム　2023/09/13
エネルギー問題解決に貢献する新しい機能性有機材料の創製 Invited

岡弘樹

九州大学薬学部講演会　2023/08/30
機能性有機材料の水素貯蔵能の開拓 Invited

岡弘樹

日本mrs水素科学技術連携研究会前期研究会　2023/07/19
クリーンエネルギー製造に向けた有機高分子の革新的触媒能の開拓 Invited

公益社団法人新化学技術推進協会（JACI）第 12 回新化学技術研究奨励賞授与式　2023/06/26
エネルギー問題に有機材料で挑む Invited

岡弘樹

技術士化学部会５月度講演会　2023/05/27
高度化する情報技術を支える革新的かつ環境適合な有機電池の開発 Invited

岡弘樹

第21回船井情報科学振興財団褒賞式　2023/05/20
有機と電気の交差点から Invited

岡弘樹

科研費変革（B）「活イオン液体の科学」キックオフミーティング　2023/04/15
バイオマスを活用した持続可能な CO2 フリー水素製造法の開発 Invited

岡弘樹

日本学術振興会令和4 (2022)年度育志賞研究発表会　2023/03/13
ポリチオフェンによる可視光照射下でのカーボンフリーグリーン水素製造法の確立 Invited

岡弘樹

倉田奨励金研究発表会　2023/03/03
持続可能な社会の実現に向けた機能性有機材料の展開～早稲田大学への感謝の気持ちとともに～ Invited

岡弘樹

第42回早桜会懇話会　2023/02/18
電荷貯蔵能を有する有機固体材料の展開

岡弘樹

有機固体若手の会 2022冬の学校　2022/12/23
育志賞受賞者講演 Invited

岡弘樹

育志賞講演会（大阪大学）　2022/11/30
エネルギー問題解決に向けた有機材料の開発 Invited

岡弘樹

早稲田大学高等学院選択科目「現代の生命科学」　2022/11/15
次世代の蓄電を担う超環境適合かつ持続可能なオール有機電池の開発 Invited

岡弘樹

大阪大学連携VC連絡会　2022/09/29
エネルギー問題解決に向けた斬新な機能性有機材料の創製 Invited

岡弘樹

京都工芸繊維大学純正・応用化学セミナー (2022年度第6回)　2022/09/14
革新的な機能性有機材料に向けた取り組み Invited

岡弘樹

京都大学人間・環境学研究科分子・生命環境論講座分子環境相関論分野分子環境相関論清秋セミナー2022　2022/09/12
最先端技術の特性から新事業開発を考える～微細藻類と水素を題材に～ Invited

岡弘樹

超異分野学会高知フォーラム　2022/08/04
持続可能な機能性有機材料に向けた取り組み Invited

岡弘樹

日東紡績株式会社 162期第1回技術講演会　2022/07/29
自己紹介と持続可能な機能性有機材料に向けた取り組み Invited

岡弘樹

産業技術総合研究所化学プロセス研究部門講演会（令和4年度第1回）　2022/07/26
環境適合な有機電池の創製 Invited

岡弘樹

令和三年度育志賞研究発表会　2022/03/02
クリーンエネルギー製造に向けた革新的触媒としての導電性高分子

岡弘樹

「第16回わかしゃち奨励賞」優秀提案発表　2022/01/27
Organic Redox Molecules for Electrochemical Selective NH4+ Recovery

Kouki Oka

MRM2021　2021/12/13
フィルム技術でエネルギーを生み出し脱炭素社会を創造する Invited

超異分野学会香川フォーラム　2021/12/03
ポリチオフェンによる可視光駆動の水分解/水素製造

第128回触媒討論会　2021/09/15
プロトン-電子のカップリングに基づくエネルギー貯蔵 Invited

第8回ハイドロジェノミクス若手スクール　2021/08/31
Organic Radicals for Thermo-electrochemical Cells

The 1st Asian Conference on Molecular Magnetism　2021/03
水素授受反応に立脚した高密度水素貯蔵を担うレドックス高分子の創出と機能開拓 Invited

令和2(2020)年度育志賞研究発表会　2021/03
有機プラスチック触媒によるオンサイト水素製造 Invited

第1回エコテックグランプリ　2020/10
水素貯蔵を可能とする高分子

第3回ハイドロジェノミクス研究会　2020/08
“コロナウイルスに打ち勝つ”究極のエコテック：有機プラスチックでの過酸化水素の製造 Invited

第9回超異分野学会本大会　2020/04
Poly(dihydroxybenzoquinone): Its High-density and Robust Charge Storage Capability in Rechargeable Acidic Polymer-air Batteries

1st INTERNATIONAL SYMPOSIUM “HYDROGENOMICS” combined with 14th INTERNATIONAL SYMPOSIUM HYDROGEN & ENERGY　2020/01
理想的な水分解: 導電性高分子の新機能 Invited

未来・水素エネルギーフォーラム in 富谷　2019/12
創蓄電デバイスの設計に向けた水素貯蔵高分子の高性能化～最新の展開～

第2回ハイドロジェノミクス研究会　2019/12
Poly(2-methyl-5-vinylpyrazine) as a Hydrogen Storage Material

The 6th Federation of Asian Polymer Societies Polymer Congress　2019/10
レドックスポリマーを負極とした有機空気二次電池

第13回超分子若手懇談会　2019/10
創蓄電デバイスの設計に向けた水素貯蔵高分子の高性能化 Invited

第4回ハイドロジェノミクス若手スクール　2019/08
FLUORENONE/FLUORENOL POLYMER NANOPARTICLES FOR REVERSIBLE HYDROGEN-FIXING AND -RELEASING WITH THE IRIDIUM COMPLEX

18th IUPAC International Symposium on MacroMolecular Complexes　2019/06
ポリ(ビニルキノキサリン)の可逆な水素化・水素発生反応

第68回高分子学会年次大会　2019/05
水素をためる高分子

第12回超分子若手懇談会　2018/10
Poly(vinylfluorenone) nanoparticles as a hydrogen carrier

第67回高分子学会年次大会　2018/05
Poly(vinyldibenzothiophenesulfone): Redox at Negative Potential

Waseda-Peking Joint Workshop on Green Innovation 2018　2018/03
ジベンゾチオフェンスルホン高分子の卑な電位での酸化還元と全有機二次電池

帝人21世紀フォーラム　2018/02
Poly(vinyldibenzothiophenesulfone): Redox at Negative Potential and Application to an Organic-based Battery

Virginia Tech-Waseda Joint Workshop on “Energy and Nanomaterials”　2017/09
ポリ(ビニルジベンゾチオフェンスルホン): 卑な電位での酸化還元と全有機二次電池

第66回高分子討論会　2017/09
Poly(vinyldibenzothiophenesulfone): Redox at Negative Potential and Application to an Organic-based Battery

7th Jilin-Korea-Waseda Alliance Annual Symposium　2017/08
Vapor Assisted Complexation: A New, Quasi Solid-state Method to High Purity Metal-complexes

17th IUPAC International Symposium MacroMolecular Complexes　2017/08
Organic-based Battery

The 3rd PKU-Waseda Joint Symposium　2017/03
ジフェニルスルホン置換ポリマーの合成と電気化学特性

日本化学会第97回春季年会　2017/03
Electrolytic Hydrogenation of Fluorenone toward Hydrogen Carrier

The 5th International Seminar on Green Energy Conversion　2016/09

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Industrial Property Rights 6

酸素及び水素の水分解による製造方法

特許7072931

Property Type: Patent
過酸化水素の製造法

Property Type: Patent
有機半導体薄膜およびその製造方法

Property Type: Patent
電極用組成物、電極および電池

Property Type: Patent
二酸化炭素の吸収又は脱着剤

Property Type: Patent
水素の製造方法

Property Type: Patent

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Research Projects 15

負極電位-電位窓ギャップの解消による無劣化二次電池の創成

山田裕貴, 岡弘樹

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 挑戦的研究(開拓)

Institution: 大阪大学

2025/06 - 2028/03
N-type Organic Semiconductor Development Through Time-Resolved Spectroscopic Characterization

2025/04 - 2027/03
持続可能なクリーンエネルギー製造に向けた革新的な有機固体触媒の創製

岡弘樹

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(B)

Institution: 大阪大学

2024/04 - 2027/03
環境適合な有機ハイドライドの創出とグリーン水素の製造・貯蔵法の構築

岡弘樹

Offer Organization: 独立行政法人環境再生保全機構(環境省)

System: 環境研究総合推進費

Category: 革新型研究開発（若手枠）

2024/04 - 2027/03
高エネルギー密度を有する高温作動長寿命リチウム系電池の開発

金村聖志, 山田裕貴, 岡弘樹他

Offer Organization: 科学技術振興機構

System: GteX（革新的GX技術創出事業）

Institution: 東京都立大学

2023/10 - 2027/03

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リチウムイオン電池のより一層の普及には、高温地域での使用を可能とする耐高温特性を有するリチウムイオン電池が必要である。リチウムイオン電池製造時のGHG削減と資源節約のためには、電池寿命を改善することが必須である。また、ドローンなどのエアモビリティーにおいては大きなエネルギー密度が求められ、金属系負極を用いるリチウム系電池の開発が必要である。これらの目標達成には、電池の高温時の挙動、劣化機構、エネルギー密度向上のための電池設計理論が重要である。そして、新規リチウム系電池を具現化するための材料技術が重要である。本チームでは、社会実装可能な電池の姿を見据えながら、材料科学・計算科学・界面科学・放射光計測を連携して。短期間・中期間・長期間に分けて3つの電池の性能を向上させていく。最終的には究極的なリチウム系電池の姿を明らかにする。
次世代の蓄電を担う超環境適合かつ持続可能なオール有機電池の開発

岡弘樹

Offer Organization: A社

System: 共同研究

2023/10 - 2026/09
高極性溶剤を用いたセルロース抽出技術および放射性セシウム除去技術開発の研究

藤田正博, 岡弘樹

Offer Organization: 特殊法人福島国際研究教育機構

Category: 令和6年度委託事業

2025/02 - 2026/03
新奇活イオン液体の設計・合成と「応用電気化学」への展開

山田裕貴, 岡弘樹

Offer Organization: 日本学術振興会

System: 科学研究費助成事業学術変革領域研究(B)

Institution: 大阪大学

2023/04 - 2026/03
高い熱電能を有する有機レドックス分子の創製と熱化学電池

岡弘樹

Offer Organization: 日本学術振興会

System: 科学研究費助成事業特別研究員奨励費

Category: 特別研究員奨励費

Institution: 大阪大学

2021/04 - 2026/03

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代表的な有機レドックス分子である有機ラジカル分子、キノン類、ビオロゲンの電気化学特性の温度依存性を確認した。熱化学電池セルによる電気化学測定法を修得し、有機レドックス分子での熱電特性（ゼーベック係数）の測定を通じて、高い熱電能を与える有機レドックス分子の創出に向けた分子要件の良好な予備知見を得て、研究開始後すぐ（準備期間）に、国際学会発表を行った。また、キノン類を対象に置換基を導入した誘導体、主鎖骨格の異なる高分子を合成し、それらが熱電能に与える影響の解明を通じて、得られた知見をもとに、高い熱電能を有する有機レドックス分子の創製に向けた今後の分子設計の指針を確立することができた。海外受入研究機関のプロジェクトに参加し、斬新な有機材料・デバイスの創製に関する技法・知見を修得した。すでに、海外受入研究者との議論により、環境適合な全有機二次電池のプロジェクトに参加している。高い酸化還元能を有する有機レドックス分子を構造内に組み込んだ有機構造体（covalent organic frameworks）を新規に合成し、同構造体を負極として用いたエネルギー密度・耐久性・環境適合性高い空気二次電池の創製に繋げている。以上のような当初の計画以上の展開について、研究内容の効果的なアピールにも尽力している。連名含む国内学会2件、国際会議2件にて研究発表し、対外的に高い評価を受けている。これらの成果は学術論文として報告予定である。
次世代の蓄電を担う超環境適合かつ持続可能なオール有機電池の開発

岡弘樹

Offer Organization: 新エネルギー・産業技術総合開発機構(NEDO)

System: 官民による若手研究者発掘支援事業(共同研究フェーズ)

2023/10 - 2025/09
The Development of Polymer Photocatalysts Directed by Introduction of Heteroatoms

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Challenging Research (Exploratory)

Institution: Kyoto Institute of Technology

2023/06 - 2025/03
次世代の蓄電を担う超環境適合かつ持続可能なオール有機電池の開発

岡弘樹

Offer Organization: 新エネルギー・産業技術総合開発機構(NEDO)

System: 官民による若手研究者発掘支援事業(マッチングサポートフェーズ)

Institution: 大阪大学

2022/10 - 2024/09
持続可能な電荷貯蔵に向けた有機・高分子レドックス材料の結合と分解の化学

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists

Category: Grant-in-Aid for Early-Career Scientists

Institution: Osaka University

2022/04 - 2024/03
Thermo-responsive molecular electrochemistry

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: The University of Tokyo

2020/04/01 - 2023/03/31
水素授受反応に立脚した高密度水素貯蔵を担うレドックス高分子の創出と機能開拓

岡弘樹

Offer Organization: 日本学術振興会

System: 科学研究費助成事業特別研究員奨励費

Category: 特別研究員奨励費

Institution: 早稲田大学

2019/04/25 - 2022/03/31

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1. 高い質量水素密度を有する有機レドックス高分子の創出コンパクト分子構造で密度高いポリビニルフルオレノールを設計・合成した。その電荷および水素（プロトン）の交換反応と水素発生（110 mL/g, 1.0 wt%）を明らかにした（Macromol. Rapid. Commun. 2019）。水素付加・脱離体をフルオレノールからキノキサリンなどの窒素複素環式化合物に拡張し、質量水素密度として有機ハイドライドと同程度の数wt%のゲル状の水素キャリアとして試験した。 2. 有機レドックス高分子での高速な水素交換反応の解明とデバイスへの展開有機レドックス高分子による高速でのプロトン・電子の交換反応を電気化学測定により明らかにした。レドックス高分子がプロトン交換反応に基づき、酸性水電解液中高い出力を有する負極材料として働くことを見出した。同高分子を負極として使用し、高い出力・耐久性をもつ有機空気二次電池をはじめて実証した（Chem. Commun. 2020、同雑誌裏表紙に選出）。スウェーデン・ウプサラ大と一部共同してレドックス高分子でのハイドロキノン/キノン間のプロトン移動に注目し、電荷輸送能と共役した過程として特徴づけ、その基礎的な電気化学特性を明らかにした。さらに、同高分子を正極、水溶液電解質を使用した高い起電力を有する有機リチウム電池の創製、実証につなげた（Electrochem. Commun. 2019）。今後も引き続きウプサラ大と共同を続け、レドックス高分子の電荷・水素の輸送能を明らかにしていく。

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Teaching Experience 17

Exercises in Organic Chemistry A　Tohoku University
Laboratory Introduction　Tohoku University
Laboratory Experiments in Chemistry B　Tohoku University
Introduction to Basic Chemistry　Tohoku University
生物有機化学特別研修　東北大学
生物有機化学特論　東北大学
応用生命化学特論　東北大学
生物有機セミナー　東北大学
有機バイオ材料化学　東北大学
学問への扉 [学部1年生対象の一般教養授業]　大阪大学全学教育推進機構
現代の生命科学（早稲田高等学院高大一貫教育事業）
有機化学実験　大阪大学大学院工学研究科
物理化学演習2（電気化学分野）　大阪大学大学院工学研究科
基礎化学実験（有機化学分野）　大阪大学大学院工学研究科
ゼミナールA・B　大阪大学大学院工学研究科
高校化学　東京都内私立高校
高校数学　東京都内私立高校

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Social Activities 4

Japan Taiwan Bilateral Workshop on Nano-Science 2022の企画・運営

Japan Taiwan Bilateral Workshop on Nano-Science 2022

2022/11/27 - 2022/11/30
キャリアディスカバリーセミナー①

2021/09/30 - 2021/09/30
育志賞講演会

2022/11/30 -
オンラインセミナー『ECO-TECH始動！〜環境問題解決と持続可能な社会を実現するテクノロジー』

2021/04/02 -

Media Coverage 11

2023年度大阪ニュークリアサイエンス協会賞受賞者のことば Myself

一般社団法人大阪ニュークリアサイエンス協会　onsanews34-1

2024/07

Type: Promotional material
研究者インタビュー

株式会社CoA Nexus　CoA Researcher　https://coanexus.com/coaresearcher/interview/kouki-oka/

2024/03

Type: Internet
市村清新技術財団、地球環境研究の助成先4件決定 Myself

日刊工業新聞社　日刊工業新聞

2024/02

Type: Newspaper, magazine
岡弘樹助教が若手研究者向け表彰を連続受賞

大阪大学大学院工学研究科　https://www.eng.osaka-u.ac.jp/ja/topics/researchresult/16870/

2023/07

Type: Internet
webページに紹介記事掲載

https://r.lne.st/adopter/27588/

2022/12

Type: Internet
雑誌表紙掲載 Myself

株式会社リバネス　研究応援 vol.26　https://lne.st/business/publishing/kenkyu/

2022/06

Type: Newspaper, magazine
高分子のミライに向けて Myself

公益財団法人高分子学会　高分子 71巻5月号

2022/05

Type: Newspaper, magazine
高分子でゼロエミッション社会の実現に挑む

早稲田大学　https://www.waseda.jp/inst/research/news/71218

2021/04
JSPS IKUSHI Prize

2021/03

Type: Other
有機プラスチックの新機能開拓（個人紹介記事）

化学工業日報

2020/12/11

Type: Newspaper, magazine
研究とは知的好奇心

株式会社リバネス　研究応援　https://r.lne.st/

2020/12

Type: Promotional material

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Academic Activities 12

独立行政法人環境再生保全機構アドバイザー

2023/04/01 - Present

Activity type: Scientific advice/Review
大阪大学外部アドバイザー

2024/04/01 - Present
日本化学会第103春季年会セッション座長

2023/03/22 - 2023/03/25

Activity type: Academic society, research group, etc.
第30回有機結晶シンポジウム

2022/11/03 - 2022/11/05

Activity type: Competition, symposium, etc.
首都圏オープン生徒研究発表会（TSEF）2022 発表審査員

2023/03/12 -
第68回高分子研究発表会(神戸) セッション座長

2022/07 -
日本化学会第102春季年会セッション座長および発表審査員

2022/03 -

Activity type: Academic society, research group, etc.
首都圏オープン生徒研究発表会（TSEF）2021 発表審査員

2022/03 -
サイエンスキャッスル関西大会ポスター審査員

2021/12 -

Activity type: Competition, symposium, etc.
首都圏オープン生徒研究発表会（TSEF）2020 発表審査員

2021/03/14 -
サイエンスキャッスル関東大会ポスター審査員

2020/12/20 -

Activity type: Competition, symposium, etc.
第13回超分子若手懇談会座長

2019/11/14 -

Activity type: Competition, symposium, etc.

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