Roles of Oxygen Species in Low-Temperature Catalytic o -Xylene Oxidation on MOF-Derived Bouquetlike CeO 2 .

To realize efficient low-temperature catalytic o -xylene oxidation, MOF-derived CeO 2 -X catalysts were prepared via the pyrolysis of MOF precursors with different ratios of cerium nitrate to trimesic acid. Among the synthesized catalysts, the bouquet like CeO 2 -1 exhibited the best activity with T 50 and T 90 of 156 and 198 °C and the lowest activation energy of 60.67 kJ·mol -1 (WHSV= 48 000 mL·g -1 ·h -1 , o -xylene concentration = 500 ppm). o -Xylene was completely mineralized, and no change in conversion efficiency or CO 2 yield was found at 5 vol % H 2 O for over 50 h. The rich active oxygen species (XPS: O sur /O latt = 0.69) and abundant oxygen vacancies (Raman: I D / I F 2g = 0.036) of CeO 2 -1 made crucial contribution to its superior catalytic activity. The O 2 -TPD and H 2 -TPR results confirmed that CeO 2 -1 had more surface active oxygen and better mobility of bulk oxygen. Moreover, the reaction routes under different atmospheres were probed through in situ DRIFTS, in which oxygen vacancy played a key role in promoting the adsorption and activation of molecular oxygen and facilitating the migration of the bulk lattice oxygen.