Enhanced Photocatalytic Activity of Hyper-Cross-Linked Polymers Toward Amines Oxidation Coupled with H2 O2 Generation through Extending Monomer's Conjugation Degree.

Visible-light-driven amines oxidation coupled with hydrogen peroxide (H2 O2 ) generation is a promising way to convert solar energy to chemical energy. Herein, a series of hyper-cross-linked polymers (HCPs) photocatalysts with different arenes monomers, including benzene (BE), diphenyl (DP), p-terphenyl (TP), or p-quaterphenyl (QP), were synthesized by simple Friedel-Crafts alkylation reaction. Owing to the maximum monomer's conjunction degree and excellent oxygen (O2 ) adsorption capacity, QP-HCPs exhibited highest photocatalytic activity for benzylamine oxidation coupled with H2 O2 generation under the irradiation of 455 nm Blue LED lamp. More than 99 % of benzylamine could be converted to N-benzylidenebenzylamine within 60 min. In addition, nearly stoichiometric H2 O2 was synchronously obtained with a high production rate of 9.3 mmol gcat -1 h-1 . Our work not only demonstrated that the photocatalytic activity of HCPs photocatalysts significantly depends on monomer's conjunction degree, but also provided a new strategy for converting solar energy to chemical energy.

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 gcat-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.