Linker engineering of benzothiadiazole and its derivative-based covalent organic frameworks for efficient photocatalytic oxidative amine coupling and hydrogen peroxide generation†

Covalent organic frameworks (COFs) have recently gained recognition as highly effective photocatalysts for solar energy conversion, in which manipulation of the electronic structures of photocatalysts is crucial for optimizing their photocatalytic performances. In this study, four benzothiadiazole and its derivative-based COFs (HIAM-0007 to HIAM-0010) were rationally designed and synthesized, which show remarkable differences toward photocatalytic oxidative amine coupling and hydrogen peroxide generation. The benzothiadiazole-based COF exhibits efficient oxidative amine coupling with a yield of up to 99%, while the naphthothiadiazole-based COF shows the highest rate of 796 μmol g⁻¹ h⁻¹ for photocatalytic hydrogen peroxide generation from air and water without additional reagents. This work underscores the variability in the activity of individual COFs across different photocatalytic reaction systems, demonstrating that the best performance is a combination of the electronic structures of COFs and the surrounding reaction environment.