Highly Active Nodules on Concave-Convex Channel Walls of Covalent Organic Frameworks for Photocatalytic Hydroperoxide Production.

Covalent organic frameworks (COFs) are promising photocatalysts for hydrogen peroxide (H2O2) production. However, the smooth channels of traditional COFs exhibit weak charge density gradients and lack highly electron-localized sites for O2 adsorption, thereby showing unsatisfactory photocatalytic performances. Herein, we present a channel wall engineering strategy to introduce nodules with high electron localization into COF channels by topological regulation. In contrast with the smooth channel walls within the traditional COFs, the nodules on the concave-convex channel walls of COFs served as active sites with an electron-rich structure and enhanced charge separation ability for the photocatalytic H2O2 production. Grafting polar carboxylic groups to the nodules further resulted in a strong built-in electric field and hydrogen bond network inside the channels, accelerating the transport of electrons and protons. The carboxylic group-grafted COF (DFH-COF) achieved a H2O2 production rate of 6075 µmol h-1 g-1 in pure water and an apparent quantum yield as high as 14.6% at 475 nm. This study provides a powerful strategy of channel wall engineering of COFs to enhance the photocatalytic performances.