The structure-activity relationship for the electron-donating functional groups in hydrazone-linked COFs and their photocatalytic H₂O₂ production

Electron-donating group modification on covalent organic frameworks (COFs) would reasonably stimulate photocatalytic activity. However, the structure-activity relationship between the electron-donating capacity and the photocatalytic activity of electron-donating functional COFs remains greatly obscure. Herein, a series of functionalized hydrazone-linked COFs containing different electron-donating capacity groups (R-COF, R = H, Me, MeO, OH) were constructed. The results suggest that the existence of substituents with strong electron-donating capacity in R-COFs can enhance the conjugation effect and thereby accelerate the separation and transfer of photogenerated electron-hole pairs. And the stronger electron-donating capacity of groups are more favorable for the electron push-pull effect, which is beneficial for photocatalytic H₂O₂ production. Among them, MeO-COF had the highest H₂O₂ generation performance without sacrificial agents under air (847.9 μmol g⁻¹ h⁻¹), which is 4.95 times higher than that of H-COF. This work provides insights for the design of functionalized COFs to achieve efficient photocatalytic H₂O₂ production.