Ni–rGO–zeolite nanocomposite: An efficient heterogeneous catalyst for one–pot synthesis of triazoles in water

An important group of pharmaceutical materials, 1,2,3-triazoles, has been synthesised using a Ni-based nanocomposite catalyst (Ni–rGO–zeolite) through azide alkyne cycloaddition (NiAAC). First, a GO–zeolite hybrid was prepared through protonation of a Na–Y–zeolite by H+ ions originating from the –COOH groups of GO. Subsequently the GO–zeolite was treated with Ni-acetate solvothermally in the presence of NaBH4 (reducing atmosphere). Under the solvothermal conditions a significant part of the incorporated Ni ions in the GO–zeolite were reduced to Ni(0) and simultaneously GO was transformed into rGO. The resulting ternary nanocomposite, Ni–rGO–zeolite, serves as a highly efficient heterogeneous catalyst, and shows excellent regioselectivity forming 1,4-disubstituted-1,2,3-triazoles as the sole product at a low loading of the nickel (∼2.6 mol% with respect to the substrate) with recyclability, and without any significant leaching of the metal. In addition, the Ni–rGO–zeolite exhibits enhanced efficiency under aqueous conditions, proficiency with varying substrates and overcomes some of the shortcomings of the previously reported limited number of Ni-based and other catalysts. The catalytic process is believed to involve the active Ni(0) species, which is stabilized by electron rich rGO that is supported on the microporous high-surface-area zeolite.