Custom-Design of Strong Electron/Proton Extractor on COFs for Efficient Photocatalytic HO Production

The development of photocatalysts with continuous electron extraction and rapid proton transfer could kinetically accelerate the artificial photosynthesis, but remains a challenge. Herein, we report the topology-guided synthesis of a high-crystalline triazine covalent organic framework (COF) decorated by uniformly distributed polar oxygen functional groups (sulfonic group or carboxyl) as the strong electron/proton extractor for efficient photocatalytic HO production. It was found that the polarity-based proton transfer as well as electron enrichment in as-obtained COFs played a crucial role in improving the HO photosynthesis efficiency (i.e., with an activity order of sulfonic acid- (SOH-COF)>carboxyl- (COOH-COF)>hydrogen- (H-COF) functionalized COFs). The strong polar sulfonic acid group in the high-crystalline SOH-COF triggered a well-oriented built-in electric field and more hydrophilic surface, which serves as an efficient carrier extractor enabling a continuous transportation of the photogenerated electrons and interfacial proton to the active sites (i.e., C atoms linked to -SOH group). As-accelerated proton-coupled electron transfer (PCET), together with the stabilized O adsorption finally leads to the highest HO production rate of 4971 μmol g h under visible light irradiation. Meanwhile, a quantum yield of 15 % at 400 nm is obtained, superior to most reported COF-based photocatalysts.