Synergetic Effect of B and O Dopants for Aerobic Oxidative Coupling of Amines to Imines

Abstract

Boron-doped mesoporous carbon material (B–C) was fabricated by annealing boric acid and sustainable cellulose at high temperature in inert atmosphere. This heteroatom-doped carbon exhibited excellent catalytic activity and high selectivity in the oxidative coupling of amine to imines. Owing to the recyclable utilization of boric acid involved in the preparation of B–C and a kind of earth abundant natural biomass being the carbon source, this metal-free carbon catalyst could be regarded as a kind of green and sustainable catalyst. Characterizations, such as X-ray photoelectron spectroscopy and X-ray absorption near edge structure, demonstrated that boron mainly existed in the form of CBO2 and functioned as catalytic active site. A proposed catalytic mechanism based on density functional theory calculations pointed out that synergistic effect of B and O atoms in CBO2 promoted adsorption and dehydrogenation of benzylamine. The intermediators, such as hydrogen peroxide, ammonia, and phenylmethanimine, could be captured by hexamethyldisilazane, indicating rationality of the proposed mechanism. This study not only developed a new catalytic system for the transformation of amine to imine, but also broadened the application of B-doped carbon materials.

Palladium Nanoparticles Anchored on Sustainable Chitin for Phenol Hydrogenation to Cyclohexanone

“…To further clarify the reasons that why Pd–chitin-150 is more active and stable during the reaction, we use XPS to analyze the atomic environment on the surface of the catalyst. For the XPS C 1s spectra of Pd–chitin- T shown in Figure a, three deconvolved peaks located at 284.5, 286.5, and 288.2 eV can be attributed to carbon atoms in the form of C–C, C–O/C–N, and N–CO, − which are similar to the XPS C 1s spectrum of pure chitin. The XPS N 1s spectra of Pd–chitin- T can be deconvolved into two peaks of N-(C) 3 and C–N–H located at 399.7 and 400.8 eV respectively .…”

Double-Shell and Flower-Like ZnS–C3N4 Derived from in Situ Supramolecular Self-Assembly for Selective Aerobic Oxidation of Amines to Imines

“…Among them, those routes based on heterogeneous photocatalysis have been considered as efficient and environmentally benign for the synthesis of imines. They represent a technology that can reduce environmental hazards and decrease energy consumption with high atom efficiency. − Thereby, we used the oxidative coupling of amines to imines under visible-light irradiation to evaluate the photocatalytic performance of the ZnS–C 3 N 4 composites. As shown in Table and Figure S7, the oxidative coupling of benzylamine (0.5 mmol) as a model substrate was carried out in the presence of molecular oxygen (as oxidant) under visible-light irradiation.…”

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts

“…In another study in 2018, Liu and co-workers 245 reported that boron-doped mesoporous carbon (B-C) can be used as a high-performance heterogeneous catalyst for the oxidative coupling of amines and the relevant imines were furnished in good to high yields and selectivity ( Scheme 33 ). This heteroatom-doped carbon was synthesized by mixing earth-abundant biomass cellulose and H 3 BO 3 , followed by annealing in an inert atmosphere at elevated temperature ( Fig.…”