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

• Published in: Nature chemistry 2018-12, Vol.10 (12), p.1180-1189
• Main Authors: Wang, Xiaoyan, Chen, Linjiang, Chong, Samantha Y., Little, Marc A., Wu, Yongzhen, Zhu, Wei-Hong, Clowes, Rob, Yan, Yong, Zwijnenburg, Martijn A., Sprick, Reiner Sebastian, Cooper, Andrew I.
• Format: Article
• Language: English
• Subjects: 639/638/298; 639/638/439/890; 639/638/77/890; Aluminum; Analytical Chemistry; Benzothiophene; Biochemistry; Catalysts; Catalytic activity; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Crystal structure; Crystallinity; Electromagnetic absorption; Evolution; Hydrogen; Hydrogen evolution; Inorganic Chemistry; Irradiation; Organic Chemistry; Organic semiconductors; Photocatalysis; Photochemicals; Photosynthesis; Physical Chemistry; Quantum efficiency; Radiation; Splitting; Thin films; Water splitting
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/s41557-018-0141-5

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. The inherent synthetic tuneability of organic materials makes them attractive in photocatalysis, but they tend to have low quantum efficiencies for water splitting. A crystalline covalent organic framework featuring a benzo-bis(benzothiophene sulfone) moiety has now been shown to exhibit high activity for photochemical hydrogen evolution from water.