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.