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Liquid-phase hydroxylation of benzene to phenol using Schiff base complexes anchored on a mesoporous organosilica support was investigated in various solvents when molecular oxygen was utilized as a green oxidant. The mesoporous organosilica support was prepared through the condensation of tetraethyl orthosilicate (TEOS) and (3-aminopropyl)triethoxysilane (APTES) in different ratios, and then Schiff base complexes were anchored on it. Various aromatic heterocycles such as imidazole, 1-methyl imidazole, pyridine, and some pyridine derivatives were used as a proximal axial ligand, and their role in the reactivity of the catalyst was investigated experimentally and theoretically. Impressive promotion of the reactivity of the catalyst was the result of this coordination. Although all the synthesized catalysts showed catalytic reactivity, the vanadyl complex showed higher activity. The results show that SiO2-Pro-Sal-VO was extremely stable concerning leaching of the vanadyl group and rendered excellent recyclability in the hydroxylation of benzene to phenol with a yield of 11.3% and selectivity of >95%. The activity of the other catalysts was as follows: SiO2-Pro-Sal-Co > SiO2-Pro-Sal-Cu > SiO2-Pro-Sal-Fe > SiO2-Pro-Sal-Zn > SiO2-Pro-Sal-Mn. [ABSTRACT FROM AUTHOR]

In the present study, Graphene Vanadic Acid (GVA) is introduced as a novel catalyst for high-efficiency hydroxylation of benzene to phenol using hydrogen peroxide at ambient conditions. Graphene oxide as a famous carbon support has converted to a high-performance catalyst through the functionalization using vanadium oxytrichloride (VOCl 3). This new carbon compound is regarded as the efficient catalyst due to the prominent advantages such as high-recativity and reusability, facile preparation, active Lewis and Bronsted acid sites, high potential for development of various oxidation reactions, and high thermal, chemical, and physical stability due to the regular carbon structure. GVA progressed the benzene oxidation toward the phenol formation as a useful raw material. Cause of the considerable reactivity of the synthesized catalyst, a minimum amount of hydrogen peroxide was required and the benzene oxidation carried out using an equimolar ratio of benzene/H 2 O 2 , and phenol obtained with a remarkable yield (28.2%) as the sole product. [ABSTRACT FROM AUTHOR]