Design of a graphene oxide-SnO2 nanocomposite with superior catalytic efficiency for the synthesis of β-enaminones and β-enaminoesters†
A graphene oxide (GO)–SnO2-based nanocomposite was synthesized by decorating the graphene oxide surface with SnO2 nanoparticles via a solvothermal process. The nanocomposite was characterized using Fourier transform infrared spectra (FTIR), FT-Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field-emission Scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM) and N2 adsorption/desorption study. The FE-SEM and TEM images demonstrate the uniform distribution of the SnO2 nanoparticles on the GO surface and high-resolution transmission electron microscopy (HRTEM) confirms an average particle size of 8–12 nm. The GO–SnO2 nanocomposite has been found to be an extremely efficient catalyst for the synthesis of β-enaminones and β-enaminoesters in methanol solvent and also, in solventless conditions. The GO–SnO2 nanocomposites exhibited synergistically more superior catalytic efficiency compared to pure graphene oxide and SnO2 nanoparticles. The reaction conditions were optimized by changing different parameters such as catalyst, solvent, catalyst loading, and temperature. It has been found that the catalyst gave higher activity under solventless conditions than methanol. The GO–SnO2 composite was recycled for up to four cycles with minimal loss in activity.