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

• Published in: Journal of colloid and interface science 2022-06, Vol.616, p.1-11
• Main Authors: Wang, Wenhui, Gao, Wei, Nie, Xinhao, Liu, Weihua, Cheng, Xiang, Shang, Ningzhao, Gao, Shutao, Wang, Chun
• Format: Article
• Language: English
• Subjects: Amines; H2O2 production; Hyper-cross-linked polymers; Photocatalytic oxidation; Sulfides
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2022.02.055

This work demonstrated that the type of crosslinkers (DCM, DCE, DMB) determine the bandgap structure of hyper-cross-linked polymers (HCPs) photocatalyst, which is crucial for the generation of reactive oxygen species and the photocatalytic activity to amines oxidation and H2O2 production. Detailed mechanism studies revealed that the excellent photocatalytic performance come from the combined effect of O2•- and 1O2. More importantly, the dynamic charge transfer process of HCPs was verified for the first time by Synchronous-illumination X-ray photoelectron spectroscopy. [Display omitted] 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.