Graphene oxide covalently functionalized with an organic superbase as highly efficient and durable nanocatalyst for green Michael addition reaction

Abstract

A highly efficient and durable nanocatalyst comprising graphene oxide (GO) covalently functionalized with an organic superbase, 1,1,3,3-tetramethylguanidine (TMG), was synthesized. Successful anchoring of TMG on the GO surface was corroborated by elemental analysis, Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDS), and Raman spectroscopy. The synthesized hybrid material (GO–Si–TMG-1) exhibited outstanding catalytic activity, comparable to that of homogeneous TMG. GO–Si–TMG-1 quantitatively promoted Michael addition reaction of malonates to various substituted nitrostyrene derivatives with excellent reaction conversions (100%) and product yields (up to 99%) under mild and green reaction conditions at 30 °C in EtOH–H2O (1:1). Moreover, the catalyst could be easily recovered by filtration and reused for at least seven times without significant decrease in catalytic performance. The catalyst recovered after seven cycles was fully characterized using various analytical techniques. In addition, the stability of the catalyst at high temperature was studied, revealing that the synthesized hybrid material could be easily applied at high temperatures without significant leaching of active sites.