MOF-derived Mn–Ce bimetallic oxide catalysts for efficient room-temperature formaldehyde oxidation

Abstract

Reducing airborne formaldehyde (HCHO) to the indoor environmental standard (0.08 mg m⁻³) 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. A new class of metal–organic framework (MOF)-derived monometallic and 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 a Petri dish (Φ = 90 mm) and the initial concentration of HCHO was regulated to 1.0 ± 0.5 mg m⁻³. The reaction temperature was set to ambient temperature (25 ± 5 °C), and the HCHO concentration measurements were performed in triplicate every 12 h. Among them, MnCe-MOF-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. Among the supported catalysts, 20 wt%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.