Abstract

Nature uses organic molecules for light harvesting and photosynthesis, but most man-made water splitting catalysts are inorganic semiconductors. Organic photocatalysts, while attractive because of their synthetic tunability, tend to have low quantum efficiencies for water splitting. Here we present a crystalline covalent organic framework (COF) based on a benzo-bis(benzothiophene sulfone) moiety that shows a much higher activity for photochemical hydrogen evolution than its amorphous or semicrystalline counterparts. The COF is stable under long-term visible irradiation and shows steady photochemical hydrogen evolution with a sacrificial electron donor for at least 50 hours. We attribute the high quantum efficiency of fused-sulfone-COF to its crystallinity, its strong visible light absorption, and its wettable, hydrophilic 3.2 nm mesopores. These pores allow the framework to be dye-sensitized, leading to a further 61% enhancement in the hydrogen evolution rate up to 16.3 mmol g−1 h−1. The COF also retained its photocatalytic activity when cast as a thin film onto a support.

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Data availability

Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition nos. CCDC 1818058 (fused sulfone diamine, FSA) and 1818059 (sulfone diamine, SA). Copies of the data can be obtained free of charge from www.ccdc.cam.ac.uk/structures/. All other data supporting the findings of this study are available within the Article and its Supplementary Information and/or from the corresponding authors upon reasonable request.

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Acknowledgements

The authors acknowledge funding from the Engineering and Physical Sciences Research Council (EPSRC) (EP/N004884/1), the European Union’s Seventh Framework Programme through grant agreement nos. 321156 (ERC-AG-PE5-ROBOT) and 692685, and the Leverhulme Trust via the Leverhulme Research Centre for Functional Materials Design. X.W. thanks the China Scholarship Council for a PhD studentship. Y.W. and W.-H.Z. acknowledge financial support from the NSFC for Creative Research Groups (21421004) and Key Project (21636002), NSFC/China and a Shanghai Oriental Scholarship. The authors thank M. Bilton for help with HR-TEM, F. McBride for help with AFM, and G.-H. Ning and H. Niu for useful discussions. The authors acknowledge the Diamond Light Source for access to beamlines I19 (MT15777) and I11 (EE12336), the ARCHER UK National Supercomputing Service, access provided via a Programme Grant (EP/N004884/1) and the EPSRC funded UK Materials Chemistry Consortium (EP/L000202/1), and the use of the facilities of the N8 HPC Centre of Excellence, provided and funded by the N8 Research Partnership and EPSRC (EP/K000225/1).

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Affiliations

  1. Department of Chemistry and Materials Innovation Factory, University of Liverpool, Liverpool, UK

    • Xiaoyan Wang
    • , Linjiang Chen
    • , Samantha Y. Chong
    • , Marc A. Little
    • , Rob Clowes
    • , Yong Yan
    • , Reiner Sebastian Sprick
    •  & Andrew I. Cooper
  2. Leverhulme Research Centre for Functional Materials Design, Materials Innovation Factory and Department of Chemistry, University of Liverpool, Liverpool, UK

    • Linjiang Chen
    •  & Andrew I. Cooper
  3. Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai, China

    • Yongzhen Wu
    •  & Wei-Hong Zhu
  4. Department of Chemistry, University College London, London, UK

    • Martijn A. Zwijnenburg

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Contributions

A.I.C. and X.W. conceived the project. X.W. synthesized the COFs and performed the characterization and photocatalysis experiments. L.C. and M.A.Z. conceived the modelling strategy and performed the calculations. S.Y.C. carried out PXRD analyses. M.A.L. carried out single-crystal X-ray structure analysis. R.S.S. performed the TCSPC experiments and co-supervised, with A.I.C., the work on COF synthesis, characterization and photocatalysis. Y.Y. collected the water sorption isotherms. R.C., X.W. and L.C. interpreted the gas sorption isotherms. Y.W. and W.-H.Z. synthesized and characterized the WS5F dye. All authors interpreted the data and contributed to preparation of the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Andrew I. Cooper.

Supplementary information

  1. Supplementary Information

    Supplementary Materials and Methods, Supplementary Characterization, Supplementary Figures 1–95; Supplementary References 1–15

  2. Crystallographic data

    CIF for SA compound; CCDC reference: 1818059

  3. Crystallographic data

    CIF for FSA compound; CCDC reference: 1818058

  4. Computational data

    Data from computational analysis of COF models and cluster models

  5. Video

    Video showing hydrogen evolution from a FS-COF thin film

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DOI

https://doi.org/10.1038/s41557-018-0141-5

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