Efficient Light Initiated One-Pot Synthesis of Benzimidazoles over PtS/ZnIn2S4 Promoted by RGO

PtS/RGO/ZnIn2S4 nanocomposites, fabricated via a rapid microwave-assisted process followed by photoreduction, were found to be an efficient multifunctional catalyst for the visible-light-driven one-pot synthesis of benzimidazoles from o-phenylenediamines and alcohols. By modulating the composition of the photocatalytic system to affect its adsorption toward the substrates and the intermediates, an optimum performance with 91.4% of 2-phenylbenzimidazole was obtained over irradiated 2.0 wt% PtS/1.0 wt% RGO/ZnIn2S4. It was revealed that the superior performance over 2.0 wt% PtS/1.0 wt% RGO/ZnIn2S4 arises from RGO, which enhances the adsorption toward benzaldehyde, the intermediate, as well as from the PtS, which promotes both alcohol dehydrogenation and intermediates condensation, to enable an efficient one-pot benzimidazole synthesis under visible light. This study reveals that in addition to the required different catalytic sites required, an efficient one-pot tandem/cascade reaction also necessitates to regulate the reaction rate of the individual reaction step, accomplished through tuning of the composition of the catalyst. This work also highlights the considerable potential of metal sulfide-based multifunctional catalysts for light-initiated one-pot tandem/cascade reactions.