MOF-derived Mn-Ce bimetallic oxide catalysts for efficient roomtemperature formaldehyde oxidation

Abstract

Reducing airborne formaldehyde (HCHO) to the indoor environmental standard (0.08 mg/m3) remains challenging when relying solely on physical adsorption. Ambient-temperature catalytic oxidation offers an effective alternative, decomposing HCHO into CO2 using high performance transition metal oxides. New type metal-organic frameworks (MOFs)-derived monometallic, bimetallic oxides and supported catalysts with different carriers were synthesized by the hydrothermal method and investigated in this study. 1.0 g of catalyst powder was dispersed uniformly on the petri dish (Φ=90 mm) and the initial concentration of HCHO was regulated to 1.0±0.5 mg/m3. The reaction temperature was set to ambient temperature (25±5°C), and the measurements for HCHO concentration were performed triply every 12 h. Among them, MnCe-MOFs-derived oxides displayed a high degradation rate (96.3%) at 48 h, with notable stability attributed to the synergistic redox cycling of Ce4+/Ce3+ and Mn3+/Mn4+, which generated abundant reactive oxygen species (ROS, O2- and ·OH), along with their excellent hydrophobicity. Electron paramagnetic resonance (EPR) analysis revealed that oxygen-deficient sites facilitate the complete oxidation of HCHO. As for supported catalysts, 20wt%MnCe-MOFs/ZSM-5 also exhibited a high oxidation activity (93.4%) ascribed to abundant active components of MnCe-MOFs, surface weak acid sites, high surface areas, and abundant oxygen vacancies, indicating high stability for HCHO oxidation.