Enhancing the potency of surface hydroxyl groups of graphene oxide for selective oxidation of benzyl alcohol

Abstract

A chemo-selective oxidation of benzyl alcohol (BzA) to benzaldehyde (BzH) was built up using transition metal immobilized amino functionalized graphene oxide [ML-f-GO (M = VO4+, Co2+, Cu2+)] as heterogeneous catalysts. Surface hydroxyl groups on GO are engaged fundamentally in the fabrication of ML-f-GO, was confirmed by density functional theory (DFT), Fourier-Transform Infrared (FTIR), electronic spectra and X-ray photoelectron spectroscopy (XPS) results, besides these X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brauner-Emmett-Teller (BET) results, Raman, scanning electron microscope (SEM) and transmission electron microscopy (TEM) were employed to corroborate the successful fabrication. DFT study was executed in an attempt to elucidate the replacement of hydroxyl groups by amino groups. The propensity of binding energy was COOH > COC>NH2 > OH which very well corroborate the belief developed from different characterization techniques that the amino groups of substituted amino functionalized moiety replace only surface hydroxyl groups of GO. Energy gap, global hardness and softness were also calculated. Catalytic aptitude of the as-prepared catalysts was weigh-up against oxidation of BzA using 30% H2O2 as a greener oxidant. The impact of distinct parameters influencing catalytic activity has also been studied. Under the optimized conditions, CuL-f-GO exclusively promoted this transformation with excellent activity to yield 99.5% BzH.