Synergistic Effect between Fe and Cu Species on Mesoporous Silica for Hydroxylation of Benzene to Phenol

Direct hydroxylation of benzene to phenol is an effective and environment-friendly route to obtain phenol. Herein, Fe-doped and cupric acetylacetonate [Cu(acac)2]-grafted mesoporous silica (Cu/Fe-SBA-15) with highly dispersed metallic sites has been synthesized and used as a heterogeneous catalyst in the hydroxylation of benzene. The physiochemical properties of the synthesized materials as well as the reciprocity between iron and copper sites were analyzed by several characterization techniques including nitrogen adsorption–desorption, X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In direct hydroxylation of benzene with H2O2 as the oxidant, the prepared Cu/Fe-SBA-15 material showed great catalytic activity. Moreover, the synergistic effect between doped Fe sites and grafted Cu sites was also investigated. In this catalyst, Fe and Cu species both played the role of active sites. Excessive activity of iron would lead to benzene peroxidation, while the presence of copper sites could effectively hinder benzene peroxidation.