Photocatalytic H2O2 production in controlled oxidative environments using covalent triazine frameworks

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.