Photodeposition of Pd nanoparticles on ZnIn2S4 for efficient alkylation of amines and ketones’ α-H with alcohols under visible light

Pd nanoparticles with a small size of ca. 6 nm were deposited on the surface of ZnIn2S4 via photoreduction of Pd(CH3CN)2Cl2 over ZnIn2S4 under visible light. The resultant Pd-ZnIn2S4 nanocomposites were fully characterized and their catalytic performance for light induced N-alkylation of amines and α-H alkylation of ketones with alcohols were investigated. It was found that Pd-ZnIn2S4 nanocomposites show superior catalytic activity for the alkylation reactions via a successful coupling of the photocatalytic dehydrogenation of alcohols over ZnIn2S4 with Pd-based hydrogenation. An optimum performance was realized over 0.5 wt% Pd-ZnIn2S4 nanocomposites by synchronization of the rates of different reaction steps in the tandem alkylation reaction. Ascribed to the small sized Pd nanoparticles, which provide more active unsaturated Pd atoms, Pd-ZnIn2S4 nanocomposites obtained via photoreduction show superior performance as compared to Pd/ZnIn2S4 obtained via a chemical reduction using NaBH4. This study provides an efficient way to realize a highly efficient and stable alkylation of amines and α-H of ketones with alcohols under visible light. This study also highlights the great potential of construction of multifunctional catalysts for light induced organic syntheses.