Oxygen-rich carbon-anchored NH₂-MIL series MOFs for room-temperature catalytic adsorption of gaseous formaldehyde and optimization through tuning hybrid composition

Catalytic adsorption is a light-free, energy-independent approach to remediate hazardous gasous compounds, such as formaldehyde (FA), by synergistically combining high adsorption capacity with intrinsic catalytic oxidation activity in the dark at room temperature (DRT). Accordingly, a design principle that couples oxygen-rich activated carbons (C-X: X = A [acid-oxidized] or P [permanganate-oxidized]) and amino functionalized MIL type metal organic frameworks (NH₂-MIL MOFs) with different metal centers (M-Y: Y = F [Fe], A [Al], or T [Ti]) is implemented to screen composite pairs for synergistic FA conversion under DRT, ambient conditions. The optimal pairing, C-A with M-T, is then formulated as CM-Z, where Z is the C-A/M-T weight ratio (in %). The air purifier (AP) constructed with CM-50 honeycomb filter exhibits superior performance against a wide range of FA concentrations (1–100 ppm). For dry FA (5 ppm), CM-50 demonstrates a clean air delivery rate of 6.92 L min^− 1 with sustained mineralization capability (~ 60% CO₂ yield) over five consecutive cycles at DRT. Mechanistically, the enhanced performance arises from an emergent, interface-enabled reaction pathway rather than a simple synergistic effect of adsorption and catalysis. Density functional theory reveals that the Ti containing NH₂ MIL (M-T) stabilizes and activates FA at Ti–O and –NH₂ sites, while the oxygen rich carbon (C-A) facilitates proton transfer across the interface. This cooperative activation is corroborated by the detection of intermediates (e.g., CH₂O₂, HCOO⁻, CO₃²⁻, H₂O, and CO₂) and by the evolution of surface elemental states in CM-50 during the filtration at DRT. This interface-enabled catalytic adsorption mechanism supports sustained FA conversion and partial mineralization without external energy input. The results position CM-basedcatalytic adsorbents as a viable, energy-independent platform for indoor air quality management.