Facile fabrication of a Cu@g-C3N4 nanocatalyst and its application for the aerobic oxidations of alkylaromatics and the reduction of 4-nitrophenol

Abstract

In this study, the preparation of a Cu@g-C₃N₄ nanocatalyst with highly active sites was developed in a facile precipitation method by the in situ reduction of Cu²⁺ adsorbed on the surface of layered graphitic carbon nitride (g-C₃N₄). The catalyst was characterized by FT-IR, XRD, SEM, TEM, ICP, XPS and BET, verifying that the Cu nanoparticles with a mean particle size of 35.89 nm were uniformly distributed onto the surface of g-C₃N₄. Alkylaromatics oxidation reactions and 4-nitrophenol reduction reactions were investigated on the Cu@g-C₃N₄ nanocatalyst with superior catalytic activity. The aerobic oxidation of ethylbenzene (EB) to acetophenone (AP) by tert-butyl hydroperoxide (TBHP) was conducted readily, and a conversion and selectivity of 98.8% and 94.0%, respectively, could be reached under optimal conditions. Moreover, the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) employing NaBH₄ has a kinetic rate constant of 1.86 × 10⁻² s⁻¹ and an activity parameter of 1.134 s⁻¹ mM⁻¹ in the presence of Cu@g-C₃N₄, which are higher values than previous results described in the literature. Repeated cycles demonstrated the outstanding recyclability and stability of the catalyst for at least four runs without a considerable loss in catalytic activity.