Synthesis of high-entropy oxides derived from metal–organic frameworks and their catalytic performance for total toluene oxidation†

In this work, a series of high-entropy oxides (HEOs) was successfully prepared by the calcination of identical metal–organic framework (MOF) precursors. Thermal treatment above 400 °C led to the complete transformation of MOFs into HEOs. The performance of the obtained HEO catalysts in the removal of volatile organic compounds (VOCs) was studied with the catalytic oxidation of toluene as the probe reaction. The optimized Ce-HEO-400 catalyst showed impressive activity and stability over toluene catalytic oxidation, which resulted from the vast quantity of surface oxygen vacancies and the relatively variable metal valence. The T₅₀ and T₉₀ values of Ce-HEO-400 were 180 °C and 255 °C, respectively. Moreover, it also showed excellent stability for 120 h with a 98.5% toluene conversion rate at 260 °C. Combined with the characterizations of XRD, SEM, TEM, BET, H₂-TPR, and XPS, it was found that the high dispersion of the active high-entropy structure and the synergistic effects of different metals are the key factors for improving the catalytic performance of the Ce-HEO-400 catalyst. This work not only presents a facile method for synthesizing HEO materials at low temperatures but also provides valuable technical support for the application of HEO catalysts in VOC removal. The findings of this study open up new possibilities for the development of efficient catalysts for the removal of VOCs.