Exciton Dipole Orientation and Dynamic Reactivity Synergistically Enable Overall Water Splitting in Covalent Organic Frameworks

Abstract

Covalent organic frameworks (COFs) are promising semiconductor photocatalysts but are still limited in overall water splitting mainly owing to a lack of clear design approaches with which to ameliorate catalytic activities. Here, we demonstrate a synergy of exciton dipole orientation and dynamic reactivity of COFs that enables water splitting for stoichiometric evolution of H₂ and O₂. The exciton dipole orientation is responsible for driving the spatial separation of photoinduced charges, while the dynamic reactivity of imine bonds of COFs with water and holes is proven for initiating water oxidation. Accordingly, a rationally designed BtS-COF with benzotrithiophene and sulfone units exhibits a much-improved performance in H₂ and O₂ evolution in neutral water under visible light. Its catalytic efficiency is even superior to some photocatalysts with metal-based water oxidation cocatalyst.