Highly efficient synthesis of imine activated by noble-metal-free CuInS2/C composite catalyst from MOFs under mild conditions

Abstract

The self-coupling reaction of primary amines is an efficient method for obtaining imines, which are important components in the organic synthesis of medicines, pesticides, and fine chemical products. However, this reaction often requires the utilization of noble metals as catalysts to achieve high yields. Therefore, it is both desirable and challenging to explore efficient noble-metal-free catalysts. In this study, a composite catalyst of CuInS2/C with a regular octahedral shape and porous framework was synthesized using the HKUST-1 as precursor. The CuInS2/C catalyst exhibited effective catalytic activity in the self-coupling synthesis of imines under mild conditions, achieving a turnover frequency (TOF) of 105 h−1, which surpasses other non-noble metal catalysts. Mechanism investigations revealed that the excellent catalytic performance of CuInS2/C was attributed to its Cu(I) center and porous structure. The former generates radicals, while the latter enhances the transport of substrates and products, facilitating imine synthesis. Importantly, the CuInS2/C catalyst could be reused at least four times and applied in gram-scale experiments, demonstrating promising practical applications. This research presents a direct approach to developing noble-metal-free and highly efficient composite catalysts for imine synthesis using MOFs as precursors.