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 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, Se) were introduced and the corresponding photoactive COFs (Py-BO-COF, Py-BT-COF and Py-BSe-COF) with distinct donor-acceptor (D-A) structure were synthesized. Experimental and theoretical studies revealed that the different heteroatoms in acceptor 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 carriers 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 that of Py-BO-COF and Py-BSe-COF, demonstrating the effect of heteroatoms on carriers separation and migration of COFs and providing some guidance for rational design of efficient photocatalysts with D-A structure for hydrogen evolution.