Windmill-Type π-Extension Within Donor Moiety of Covalent Organic Framework Boosts Overall Photocatalytic Hydrogen Peroxide Production.

Abstract

Covalent organic framework (COF)-based catalysts are promising for overall photocatalytic hydrogen peroxide (H2O2) production, yet the sluggish kinetics of water oxidation reaction (WOR) and inefficient charge carrier processes limit the catalytic performance. Herein, by modulating the donor structure of COF where the WORs take place, we designed and synthesized a new benzothiophene-based donor moiety (BTPC) with intramolecular windmill-type π-extension to simultaneously enrich WOR active sites and enhance charge carrier separation. The BTPC-based COFs exhibited remarkably enhanced photocatalytic H2O2 production performance compared with the conventional benzotrithiophene-based COF (BTT-TAT). Notably, BTPC-TAT achieved a rate of 9.08 mmol g-1 h-1, which is over 3-fold higher than that of BTT-TAT (2.94 mmol g-1 h-1). In the following continuous-flow H2O2 generation system, the immobilized BTPC-TAT also exhibited excellent stability and facile operation for in situ H2O2 generation coupled with Rhodamine B degradation. Comprehensive studies demonstrate that the "windmill-type π-extension" strategy in the donor moiety promotes charge carrier separation and prolongs carrier lifetime, while enhancing WOR interfacial interactions via improved water adsorption and reduced energy barriers for intermediate formation. This work introduces a new donor moiety for efficient photocatalytic H2O2 production and provides insights into rational intra-donor π-system engineering.