Improving Mass Transport and Charge Transfer in COF‐Based Photocatalysts with Three‐Dimensional Ordered Macropores for Benzylamine Oxidation and Hydrogen Evolution

Abstract

Covalent organic frameworks (COFs) have shown promise as photocatalysts for chemical transformations. However, their dense micropores and poor pore connectivity hinder mass transport and charge separation/transfer, limiting their efficiency. Herein, we develop a one-step self-sacrificing template strategy to synthesize three-dimensional ordered macroporous COFs (3DOM-COFs). This approach uniquely integrates in situ Tp–Tta COF crystallization with synchronized degradation of polystyrene templates under solvothermal conditions. This method introduces unreported kinetic match between template decomposition and framework growth. Such a confined growth mechanism leads to structurally robust and highly ordered macroporosity without post-processing. 3DOM architecture enables uniform dispersion of fine ZnCdS nanoparticles for the generation a 3DOM-COF based S-scheme heterojunction, which exhibits remarkable performance in the oxidation of benzylamine (BA) for simultaneous N-benzylbenzaldimine production with 99% selectivity at a rate of 15.1 mmol g−1 h−1 and H2 generation with a rate of 17.8 mmol g−1 h−1. The 3DOM architecture confers 50-fold faster mass transport than bulk COFs, while the heterojunction facilitates directional charge separation and interface charge transfer. Density functional theory calculations confirm that the heterojunction optimizes reaction thermodynamics by lowering the potential energy barriers of BA activation. The work pioneers a template-concurrent synthesis paradigm, resolving COFs' critical pore engineering challenges.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor