Polyoxometalate on functionalized graphene sheets as a hybrid catalyst for efficient synthesis of benzimidazoles

In this work, graphene oxide (GO) nanoparticles were synthesized and subsequently modified using 3-aminopropyltrimethoxysilane (APTMS). An Anderson-type polyoxometalate [(C₄H₉)₄N]₂[CrMo₆O₁₈(OH)₆] was then immobilized on the surface of the modified graphene oxide nanoparticles. The obtained catalyst was characterized using Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). The catalytic performance of this recyclable hybrid catalyst was evaluated for the synthesis of benzimidazole derivatives at 75 °C under solvent-based conditions. The hybrid catalyst demonstrated easy separation and could be successfully reused at least six times with only a slight reduction in the yield of the desired product. Leaching and recovery tests, along with FT-IR analysis, confirmed the high stability of the catalytically active species and the heterogeneous nature of the catalyst.