Photocatalytic selective amines oxidation coupled with H₂O₂ production over hyper-cross-linked polymers

Herein, a series of hyper-cross-linked polymers (HCPs) photocatalysts were synthesized through Friedel-Crafts alkylation reaction, in which benzene served as monomer and dichloromethane (DCM), dichloroethane (DCE) as well as 1,4-dimethoxybenzene (DMB) served as crosslinker. It was found that different crosslinker can change the energy level of conduction and valence band of HCPs, which is crucial for the generation of reactive oxygen species (ROS), and the separation efficiency as well as mobility of photo-generated carriers. Among of these prepared HCPs photocatalysts, DCM-HCPs exhibited highest conversion and selectivity toward benzylamine oxidation under the irradiation of blue LED lamp (455 nm) and sunlight in air atmosphere. The highest apparent quantum yield (AQY) of DCM-HCPs is 0.44%. More importantly, a high yield of H₂O₂ (TOF = 5712.67 μmol g_cat^-1 h^-1) was synchronously obtained during the process of benzylamine oxidation. Synchronous-illumination X-ray photoelectron spectroscopy (SI-XPS) was used to investigate the charge transfer mechanism of HCPs. The results revealed that the photoelectrons transferred from crosslinker (-CH₂-) to benzene ring for inducing benzylamine oxidation to N-benzylidenebenzylamine and H₂O₂ production. In addition, a series of amines and sulfides can also be smoothly oxidized at the similar conditions.