The Hydration-Initiated Pathway of Water Oxidation over Photoexcited Covalent Organic Frameworks

A hydration-initiated pathway of photocatalytic water oxidation over covalent organic frameworks (COFs) is proposed. The hydration of water addition to the hydrazone unit of hydrophilic COF efficiently induces the initial step of photocatalytic water oxidation. The subsequent oxidative deprotonation and the coupling of the bonded hydroxyl radicals selectively yield H2O2. Oxidative deprotonation is identified as the rate-determining step, which can be facilitated by electron and proton capture. An excellent H2O2 production rate of 1.0 mmol g–1 h–1 was achieved in pure water under atmospheric conditions. This study provides a mechanistic insight into water oxidation over COFs.