The modulation acceptor of covalent organic frameworks: the optimization of intramolecular and interfacial charge transfer processes

Abstract

Solar-driven water splitting for hydrogen evolution is one of the effective ways to alleviate environmental pollution and energy crisis. Covalent organic frameworks (COFs), as new platforms for solar-to-chemical energy, have drawn much attention owing to their pre-designable structures and tailor-made functions. Herein, three acceptor units containing different heteroatoms (O, S, and Se) were introduced and the corresponding photoactive COFs (Py-BO-COF, Py-BT-COF and Py-BSe-COF) with distinct donor–acceptor (D–A) structures were synthesized. Experimental and theoretical studies revealed that the different heteroatoms in acceptors affect the intramolecular and interfacial charge transfer and also significantly affect the valence state and deposition site of co-catalyst platinum. Py-BT-COF, with the best exciton separation ability and interfacial carrier migration ability, exhibits the highest hydrogen evolution rate (HER) up to 10.00 mmol g⁻¹ h⁻¹, which is 1.8 and 82 times than Py-BO-COF and Py-BSe-COF, demonstrating the effect of heteroatoms on carrier separation and migration of COFs and providing some guidance for the rational design of efficient photocatalysts with the D–A structure for hydrogen evolution.