Enhanced Photocatalytic Production of Hydrogen Peroxide by Covalent Triazine Frameworks with Stepwise Electron Transfer

Abstract

The photosynthesis of hydrogen peroxide (H₂O₂) from pure water and oxygen using metal-free photocatalysts offers a renewable approach to convert solar energy to storable chemical energy. However, the efficiency of H₂O₂ photosynthesis is often hindered by the rapid recombination of photogenerated charge carriers. Herein, we present an elegantly designed covalent triazine framework (CTF) photocatalyst, denoted as Ace-asy-CTF, with a stepwise electron transfer pathway for the highly efficient photosynthesis of H₂O₂. Notably, Ace-asy-CTF possesses localized excited-state charge distribution and stepwise electron transfer that is created by the weakly conjugated acetenyl units in the asymmetric frameworks, as revealed by transient spectroscopies and further supported by theoretical calculations. Meanwhile, the introduced acetenyl units also serve as active sites for the oxygen reduction reaction (ORR). The simultaneously enhanced stepwise charge transfer and two-step 2e^– ORR in Ace-asy-CTF result in an excellent H₂O₂ yield of 2594 μmol g^–1 h^–1, directly produced from oxygen and pure water without requiring any sacrificial reagents. This work paves the way for the development of next-generation metal-free catalysts, providing a feasible benchmark for the highly efficient and stable photosynthesis of H₂O₂.