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, N₂ 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 (T₉₀ = 225 °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.