Metal–organic framework/carbon nitride nanosheets composites (TMU-49/CNNSs): efficient photocatalyst for aerobic oxidation of alcohols under visible light

Abstract

Oxidation reactions are considered as a challenging issue at the industrial scale. As several traditional methods are not biocompatible and safe, there is a need to develop sustainable photocatalytic approaches that employ molecular oxygen as the terminal oxidant. Herein, a cobalt-based metal–organic framework (MOF) was hybridized with graphitic carbon nitride nanosheets (CNNSs), namely TMU-49/CNNSs, using a facile in situ ultrasound-assisted synthesis, for the catalytic photo-oxidation of benzyl alcohol under visible light irradiation. The oxidation was carried out with variation of four parameters: solvent, catalyst amount, time and light source. Characterization of as-prepared samples was performed by Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray powder diffraction, N₂ adsorption–desorption, scanning electron microscopy, and UV-visible diffuse reflection spectra. The TMU-49/CNNSs composite exhibited remarkable photocatalytic activity under visible light irradiation; the oxidation yield reached almost 80% for benzyl alcohol after 3 h reaction. The superior photocatalytic activity of the MOF/CNNSs composite is attributed to enhanced separation of the photogenerated electron–hole pairs and increased visible-light absorption.