Oxygen-mediated formation of MoS_x-doped hollow carbon dots for visible light-driven photocatalysis

It is of great interest to modulate the photocatalytic activity of nanomaterials by varying their composition at the atomic scale and their nanostructure. Herein, we demonstrate a bottom-up approach for the synthesis of MoS_x-doped hollow carbon dots (_MoSHCDs) as a photocatalyst for the visible light-driven aerobic oxidative coupling of amines. The molecular oxygen-assisted solvothermal reaction of a MoS₂ nanosheets/N-methyl-2-pyrrolidone dispersion provided _MoSHCDs with a unique hollow interior of 6-7 nm as well as with doping of a large portion of pyridinic N atoms and MoS_x. As compared to typical carbon dots not bearing hollow structures, the as-prepared _MoSHCDs exhibited excellent photocatalytic activity in the oxidative coupling reactions of various amines under visible light irradiation at 25 °C. Mechanistic investigations suggested that doping with pyridinic N atoms and MoS_x was responsible for the significantly improved photocatalytic activity of _MoSHCDs in photocatalysis. The reaction mechanism of the oxidative coupling reactions of amines that were effectively promoted by _MoSHCDs under visible light irradiation was also fully examined.