Covalent organic frameworks with spatially separated triad architecture for sacrificial agent–free H2O2 photosynthesis

Abstract

In situ H2O2 activation is crucial for energy and environmental applications. However, conventional photocatalysts suffer from severe charge recombination and poorly defined redox sites, which limit efficient and sustainable H2O2 production. Herein, we present a triad architecture covalent organic framework (TpA–TzA) where spatial separation of the thiophene-based oxidation center and benzothiadiazole-based reduction center, bridged through planar-conjugated triazine linkers, enables directed electron–hole shunting. Within this triad architecture, the thiophene unit drives water oxidation (4e⁻ WOR), producing O2 and protons that are transferred through the Brønsted-basic triazine bridge. This proton transfer enables the benzothiadiazole unit to perform a highly selective 2e⁻ ORR via the key *OOH intermediate. This spatially separated design extends the charge-carrier lifetime to 3.26 ns and synergistically enhances the built-in electric field and interfacial mass transport. A remarkable H2O2 production rate of 9746.2 μmol h−1 g−1 is achieved without sacrificial agents, which is nearly twice those of binary COFs (TpA–TMT), along with remarkable cycling stability and broad pH adaptability.