Sulfone-containing covalent organic frameworks for photocatalytic hydrogen evolution from water

Wang, Xiaoyan and Chen, Linjiang and Chong, Samantha Y. and Little, Marc A. and Wu, Yongzhen and Zhu, Wei-Hong and Clowes, Rob and Yan, Yong and Zwijnenburg, Martijn A. and Sprick, Reiner Sebastian and Cooper, Andrew I. (2018) Sulfone-containing covalent organic frameworks for photocatalytic hydrogen evolution from water. Nature Chemistry, 10 (12). pp. 1180-1189. ISSN 1755-4330 (https://doi.org/10.1038/s41557-018-0141-5)

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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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