Triazine-cored donor–acceptor covalent organic framework promotes highly efficient photocatalytic synthesis of H2O2†

Abstract

Covalent organic frameworks (COFs) have emerged as highly promising photocatalysts for hydrogen peroxide (H₂O₂) production due to their flexible structural designability and π–π conjugated backbone. However, the limited efficiency of electron–hole pair separation during COF photocatalysis remains a major challenge. Herein, a donor–acceptor (D–A) type COF containing a triazine functional group, namely TPB–TPT-COF, was concisely designed and synthesized for H₂O₂ production via photocatalysis. Owing to its enhanced carrier separation and transport, TPB–TPT-COF exhibited a remarkable H₂O₂ production rate of 6740 μmol g⁻¹ h⁻¹ from pure water and oxygen without any sacrificial agent under visible light irradiation, which is three times higher compared to its isomeric TPB-COF. Further experimental and theoretical investigations revealed that the photocatalytic processes of TPB–TPT-COF proceed via dominant 2e⁻ oxygen reduction reaction (ORR) pathways (O₂ → ˙O₂⁻ → H₂O₂ and O₂ → ˙O₂⁻ → ¹O₂ → H₂O₂) and 4e⁻ water oxidation reaction (WOR) pathways. This study not only elucidates the impact of the D–A structure on the activity within photocatalytic reactions but also provides novel design strategies for the improvement of photocatalytic H₂O₂ production.