Benzimidazole-based covalent organic framework embedding single-atom Pt sites for visible-light-driven photocatalytic hydrogen evolution

Visible-light-driven photocatalytic hydrogen evolution reaction (HER) over a semiconductor provides an effective avenue to produce renewable clean energy and alleviate energy and environmental crises. However, the HER efficiency is still limited by the sluggish electron transfer process. Herein, a highly active covalent organic framework (COF) was constructed from the unusual benzimidazole monomer in a microwave-assisted solvothermal pathway. With single-atom Pt sites as cocatalyst, the catalyst exhibited an HER rate up to 115 mmol g–1 h–1 and a high turnover frequency of 4475.1 h–1 under visible-light irradiation. The above performance relied on the combination of benzimidazole moieties and COF framework, which, on the one hand, stabilized photogenerated electrons to prolong the electron lifetime, and on the other hand provided a strong host-guest interaction that resulted in the creation of single-atom Pt sites and the acceleration of the electron-transfer to the active sites for proton reduction. This work demonstrates the perspective of electron stabilization and interfacial charge transfer avenue construction in the HER process, which can be reached by a molecular-level design of COF-based organic semiconductors by using structural and functional diverse asymmetric building blocks.