Efficient heterogeneous photocatalytic C–C coupling of halogenated arenes mediated by metal cocatalyst

Abstract

Heterogeneous photocatalysis offers an eco-friendly platform for selective C–C coupling of benzyl halides via hydro-dehalogenation by employing alcohols as the hydrogen donor, yet the reaction rate under visible light irradiation needs significant enhancement for applications. This calls for a designed and affordable photocatalyst with optimized adsorption and kinetics for the selective conversion of reactants and intermediates. Here we demonstrate that choosing an optimal metal as cocatalyst supported on the graphitic carbon nitride (gCN) photocatalyst, the adsorption of benzyl halide, the activation of the C–X bond, and the removal kinetics of photogenerated active halogen species can be manipulated to tune the generation rate of bibenzyl. In comparison with Pd and Cu, Ni supported on gCN presents a moderate adsorption of benzyl halide, a fast C–X dissociation rate, and a rapid removal of active halogen anions, thus achieving a 13-fold enhancement for C–C coupling of halogenated arenes under visible light irradiation. Such high performance also makes it a promising photocatalyst for scalable synthesis of value-added bibenzyls in a flow system.