Zeolitic Imidazolate Framework-67-Derived CeO2@Co3O4 Core-Shell Microspheres with Enhanced Catalytic Activity toward Toluene Oxidation

In this work, a core-shell structured CeO2@Co3O4 catalyst was successfully prepared by using a zeolitic imidazolate framework-based material as a sacrificial template. The structure, morphology, and physicochemical characteristics of these materials were investigated by X-ray diffraction, N-2 sorption, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and temperature-programmed reduction studies. Compared with pure Co3O4 and CeO2, the CeO2@Co3O4 sample displayed superior catalytic performance (T-90 = 225 degrees C) toward toluene oxidation. Results demonstrated that the CeO2@Co3O4 sample exhibited a core-shell structure, with hierarchically wrinkled surfaces. This unique structure, especially the interface between the core and the shell, endowed the CeO2@Co3O4 catalyst with better activity. In addition, there was a synergistic effect between cerium and cobalt oxides in the core-shell bimetallic sample, which was responsible for the improved performance of the material. Moreover, surface-active oxygen species involved and played a significant role in toluene oxidation.