Isomerization of Covalent Organic Frameworks for Efficiently Activating Molecular Oxygen and Promoting Hydrogen Peroxide Photosynthesis.

Constitutional-isomerized covalent organic frameworks (COFs), constructed by swapping monomers around imine bonds, have attracted attention for their distinct optoelectronic properties, which significantly impact photocatalytic performance. However, limited research has delved into the inherent relationship between isomerization and the enhancement of HO photosynthesis. Herein, a pair of isomeric COFs linked by imine bonds (PB-PT-COF and PT-PB-COF) is synthesized, and it is proved that isomeric COFs exhibit different rate-determining steps in the generation process of HO, resulting in a twofold increase in photocatalytic efficiency. Specifically, PT-PB-COF demonstrates effective adsorption and activation of molecular oxygen (O + e → •O + e → HO), leading to a significant improvement in HO photocatalytic efficiency. In contrast, PB-PT-COF exhibits robust interaction with HO, enabling direct oxidation of HO (HO + h → HO). This study provides a thorough understanding of the intrinsic mechanism underlying the constitutional-isomerized COFs in the photocatalytic HO generation, offering insights for further optimizing building units.