ZnO/COF S-scheme heterojunction for improved photocatalytic H2O2 production performance

Covalent organic frameworks (COFs) are burgeoning crystalline porous materials with great potential in photocatalysis, but their applications are mainly restricted by the speedy recombination rate of charge carriers. Herein, a step-scheme heterojunction ZnO/COF(TpPa-Cl) is fabricated by a simple electrostatic self-assembly method, and its photocatalytic H2O2 production performance is also investigated. The S-scheme heterojunction between ZnO and TpPa-Cl contributes to enhanced light absorption, promoted reactant adsorption capacity, increased redox power, and efficient separation and transfer of photogenerated charge carriers, leading to an improved photocatalytic H2O2 evolution activity. The optimal composite possesses the maximum H2O2 evolution rate of 2443 mu mol.g(-1).h(-1) under simulated solar light irradiation, which is about 3.3 and 8.7 times higher than pristine ZnO nanoparticles and TpPa-Cl, respectively. Moreover, the charge transfer pathway in S scheme heterojunction photocatalysts is well elucidated. This investigation provides designing guidelines in the construction of other COF-based S-scheme heterojunctions.