Pristine Graphene–Copper(II) Oxide Nanocatalyst: A Novel and Green Approach in CuAAC Reactions

Abstract

Pristine graphene, as the name suggests is the closest to graphite structurally among all the forms of graphene that are synthesized using different methods. High electronic conductivity, large surface area, and absence of defects make this perfect two-dimensional arrangement of sp2 hybridized carbon atoms a perfect support material for metal or metal oxide nanoparticles. We have introduced a quick and green route to synthesize CuO nanocomposites having pristine graphene as a support material by microwave assisted hydrothermal reaction. The nanocomposite exhibited very high catalytic activity in copper catalyzed azide-alkyne cycloaddition (CuAAC) reactions compared with reduced graphene oxide (RGO)-CuO nanocomposite and CuO nanoparticles. The presence of pristine graphene in the nanocomposite increases the catalytic activity due to its better conductivity and ability to adsorb reactants through π–π interaction than RGO. The pristine graphene-CuO nanocomposite showed very good recyclability with much less leaching of the metal from it. The CuAAC reactions could be completed in a short duration (1 h), at low reaction temperature (30 °C), using water as a “green” solvent with a small amount of the pristine graphene-CuO nanocomposite as catalyst (0.51 mol %) and sodium ascorbate as cocatalyst (1 mol %).