Bimetal oxide CuO/Co3O4 derived from Cu ions partly-substituted framework of ZIF-67 for toluene catalytic oxidation

Abstract

A MOF-templated method is developed to prepare bimetal oxide CuO/Co3O4 by in situ pyrolysis of Cu2+ partly-substituted ZIF-67 precursor. The physicochemical properties of CuO/Co3O4 are studied by various characterizations such as X-ray diffraction, Raman analysis, transmission electron microscope, scanning electron microscope, N2 adsorption-desorption measurement, X-ray photoelectron spectroscope, O2 temperature-programmed desorption, H2 temperature-programmed reduction, etc. Comparison with CuO, Co3O4 and Mix-CuO/Co3O4, 90 % of both toluene conversion and mineralization over CuO/Co3O4 are fulfilled at around 229 °C under the condition of 1000 ppm toluene and weight hour space velocity =20,000 mL/(g h), which is promoted more than 40 °C. The better catalytic performance of CuO/Co3O4 attributes to high mutual dispersion of two oxides, porous structure, lower temperature reducibility, abundant lattice defects, more active oxygen species, higher Co3+/Co2+ and Olatt/Oads molar ratios. Meanwhile, CuO/Co3O4 exhibits a better catalytic stability at different conversions and a good tolerance to 10 vol.% of water vapour. The investigation of temperature-dependent active oxygen species and in-situ DRIFTS results reveal that toluene oxidation on CuO/Co3O4 obeys Mars van Krevelen mechanism.