Preparation, characterization and catalytic oxidation properties of silica composites immobilized with cationic metalloporphyrins

Abstract

Herein, the metalloporphyrins Co(II) (5, 10, 15, 20-tetra (4-(3-(N-ethyl-4-pyridyl)pyrazolyl)phenyl)porphyrin) (CoTEtPyP) and Mn(III) (5, 10, 15, 20-tetra(4-(3-(N-ethyl-4-pyridyl)pyrazolyl)phenyl)porphyrin) (MnTEtPyP(OAc)) were synthesized and characterized spectroscopically. The cationic metalloporphyrins were firstly immobilized on the surface of SiO2 by electrostatic attractions with hydrothermal method to get the gels. Then, the gels were extracted by supercritical CO2 to remove the redundant solvent molecules and the unreacted metal salt. The structures and properties of porphyrin–SiO2 porous composites (PSC1 and PSC2) were characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, transmission electron microscope, powder X-ray diffraction, thermalgravimetric analysis and nitrogen sorption measurements. N2 absorptions have verified that the porous materials have large BET surface area and big N2 uptake capacity. The composites also have shown higher specific surface area and superior thermal stability. The catalytic activities of the new PSCs to the ethylbenzene oxidation carried out indicated that both of them exhibit highly selectivity of acetophenone (> 99%) with the conversion of 87.6% (PSC1) and 93.0% (PSC2), respectively.