Comparative Study of Catalytic Oxidation of Toluene over Porous Metal Oxide Catalysts Derived from (Mn, Ce, Co)-MOFs

This study presents a systematic investigation into the catalytic oxidation of toluene using metal-organic framework (MOF)-derived porous metal oxide catalysts obtained through controlled pyrolysis. The MOF-derived catalysts (Mn3O4-BTC, CeO2-BTC, Co3O4-BTC) demonstrated remarkable improvements in catalytic activity and stability compared to their commercial counterparts (Mn3O4-c, CeO2-c, Co3O4-c), achieving 90% toluene conversion (T90) at significantly lower temperatures of 240 °C, 241 °C, and 237 °C, respectively. Besides, a comprehensive suite of characterization techniques was employed to elucidate the structure-activity relationships. Specifically, various traditional and in situ characterization techniques, including X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2 programmed reduction (H2-TPR), online-tandem thermogravimetry-mass spectrometry (online-tandem TG-MS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), were employed to elucidate crystallinity, porosity, morphology analysis, probe surface chemistry, redox properties, real-time tracking of thermal decomposition, and reaction mechanisms during the catalytic oxidation of toluene. It was found that the enhanced catalytic performance could be attributed to the synergistic effects of a high surface area, well-dispersed active sites, and abundant oxygen vacancies. These insights provided fundamental insights into the design and optimization of MOF-derived catalysts for efficient volatile organic compounds (VOCs) abatement in environmental catalysis.