Mn-MOFs with Different Morphologies Derived MnOx Catalysts for Efficient CO Catalytic Oxidation

The design of efficient catalysts is vital for the application of catalytic oxidation technology in the removal of gaseous pollutants. Herein, a series of MnOx catalysts with the typical Mn2O3 crystal structure was synthesized via the high-temperature pyrolysis method by using Mn-based metal–organic frameworks (Mn-MOFs) with various morphologies as the precursors. The physicochemical properties of these Mn-MOF-derived MnOx samples were investigated by various characterization techniques, including X-ray diffraction (XRD), thermogravimetry (TG), N2 adsorption–desorption, scanning electron microscope (SEM), and H2 temperature-programmed reduction (H2-TPR), and their catalytic activity was evaluated for catalytic CO degradation. The results showed that the Mn-MOF with leaf-like morphology, derived MnOx-Leaf, presented the optimal catalytic CO oxidation performance (T98 = 214 °C), stability, and reusability. Characterization results showed that the different Mn-MOF-derived MnOx catalysts possessed different physical–chemical properties. The superior catalytic activity of MnOx-Leaf for CO degradation was ascribed to its large surface area and pore size, better low-temperature redox properties, and high H2 consumption, which promoted the adsorption and activation of the CO and gaseous oxygen molecules, improving CO oxidation. Finally, the possible CO degradation pathway was evaluated by in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), which showed that gaseous CO and O2 were adsorbed on the surface of the catalyst and oxidized to form surface carbon-related species (bicarbonate and carbonate), and finally converted to CO2.