Efficient Photocatalytic Selective Oxidation of Benzylamines over Cobalt Molecular Catalyst Covalently Bonded to Carboxyl Functionalized Carbon Nitride

Abstract

Photocatalysis is accepted as a promising method for selective oxidative coupling of amine to imine. However, owing to the rapid dehydrogenation of the generated imine intermediate of α‐amino hydrogen to butyronitrile, it remains a huge challenge to fabricate an exquisite catalyst with enhanced conversion and selectivity. Herein, a novel heterogeneous catalyst (Bpy‐CoCl2/CNCOOH) is developed, where carboxyl functionalized carbon nitride (CNCOOH) serves as a substrate material and couples with highly efficient cobalt‐aminopyridine (Bpy‐CoCl2) molecular catalyst through covalent bonding. The catalyst not only effectively facilitates the transfer of photogenerated charges, but also generates mildly oxidatively active species of superoxide radicals, which can effectively oxidize various functionalized benzylamines to corresponding imines in the presence of oxygen with at least 78.5% conversion and >99% selectivity using O2 as oxygen source, especially for the unmodified benzylamine with >99% conversion and >99% selectivity. This unique combination of a selective molecular catalyst and a simple and robust semiconducting material open new avenues for the selective oxidative coupling of amines.

Keywords

• benzylamine
• carbon nitrides
• covalent bonding
• molecule catalysts
• photocatalytic selective oxidation