Photocatalytic H2O2 production in controlled oxidative environments using covalent triazine frameworks

Abstract

An emerging sustainable technology for the photocatalytic synthesis of hydrogen peroxide (H2O2) from molecular oxygen and sunlight has garnered significant research interest. The addition of sacrificial agents often enhances O2 reduction for H2O2 production but also results in the accumulation of their oxidized impurities in the reaction media. Exploring photo-oxidative reaction designs, therefore, is critical to improving photocatalytic H2O2 production. Herein, we report that controlling oxidative reaction media makes a significant difference in photocatalytic H2O2 production. The challenging toluene oxidation could be integrated with photocatalytic O2 reduction, co-producing H2O2 as well as benzaldehyde. Covalent triazine frameworks (CTFs) were selected as platform photocatalysts, where the CTF with a thiophene linker exhibited a high H2O2 production (105 µmol) with toluene oxidation under simulated sunlight, which was 4.7- and 2.5-fold higher than that observed with H2O (22.3 µmol) and H2O/alcohol (42.4 µmol) oxidation, respectively. The theoretical calculation reveals that the binding affinities of toluene and O2 on CTF surfaces enable the simultaneous production of benzaldehyde and H2O2, respectively. A dual-phase system composed of toluene and water layers allows simple separation of the two products with high purity. Our finding demonstrates the crucial influence of oxidative environments in photocatalytic O2 reduction, showing the potential of toluene photo-oxidation as a cooperative reaction medium for H2O2 production.