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

A MOF-templated method is developed to prepare bimetal oxide CuO/CoO by in situ pyrolysis of Cu partly-substituted ZIF-67 precursor. The physicochemical properties of CuO/CoO are studied by various characterizations such as X-ray diffraction, Raman analysis, transmission electron microscope, scanning electron microscope, N adsorption-desorption measurement, X-ray photoelectron spectroscope, O temperature-programmed desorption, H temperature-programmed reduction, etc. Comparison with CuO, CoO and Mix-CuO/CoO, 90 % of both toluene conversion and mineralization over CuO/CoO 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/CoO attributes to high mutual dispersion of two oxides, porous structure, lower temperature reducibility, abundant lattice defects, more active oxygen species, higher Co/Co and O/O molar ratios. Meanwhile, CuO/CoO 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/CoO obeys Mars van Krevelen mechanism.