Heterogeneous visible-light photoredox catalysis with NiCl2@g-C3N4 for induced C(sp2)-H/NH cross-dehydrogenative coupling

Abstract

A novel photoactive NiCl₂@g-C₃N₄ catalyst system, which effectively drives C(sp²)-H/NH bond formation between quinolin-2(1H)-ones, primary and secondary aliphatic amines under blue light irradiation. The NiCl₂@g-C₃N₄ composite with a NiCl₂ loading of 0.7wt% had the highest photoactivity, and the calculated band gap energy value is 2.56 eV The nickel ion could act as an electron acceptor enhancing carrier separation and transfer efficiency, greatly enhanced the photoreaction efficiency of g-C₃N₄. Preliminary mechanistic studies indicate upon visible light irradiation, the photo-generated electrons and holes act as oxidants, thereby generating amine radicals in the absence of external chemical oxidants. This provides a straightforward and efficient approach for directly 3-aminating quinoxalines-2(1H)-ones. Moreover, the heterogeneous catalyst can be recycled at least six times without significant activity loss.