Aldehyde-philic Portal Engineering of γ-Cyclodextrin MOF for Synergistic Capture of Toluene and Formaldehyde in Humid Atmospheric Environments

Efficient removal of multicomponent volatile organic compounds (VOCs) from real environments remains challenging, particularly under humidity. This study introduces an “aldehyde-philic portal modification” strategy that precisely anchors dopamine (DA) at γ-cyclodextrin-based metal–organic framework (γ-CD-MOF) outer rim via H-bonding to construct oligomeric polydopamine (o-PDA) structures. This pore design partitions the cyclodextrin cavity into an aldehyde-philic outer rim and arene-philic interior for efficient synergistic capture of formaldehyde and toluene in humidity. Exposed pyrrolic N sites on o-PDA enable γ-CD-MOF@PDA2 to preferentially bind CH2O, which then act as new sites to enhance subsequent C7H8 capture via CH−π interactions while hindering H2O binding to peripheral hydroxyls and preventing large-sized water clusters from blocking cavity openings. Furthermore, the hydrophobic inner cavity exhibits strong π–π conjugation with C7H8, facilitating its diffusion and establishing an “outer capture–inner fixation” pathway, significantly enhancing toluene capacity. At ∼40% relative humidity, the toluene working capacity of γ-CD-MOF@PDA2 in the multicomponent system increased by 106% over the single-component system, while the formaldehyde capacity remained unchanged. Consequently, the total working capacity of toluene and formaldehyde reached twice the sum of their single-component adsorption capacities, demonstrating marked synergistic coadsorption. This work provides a feasible approach for controlling multicomponent VOCs in complex humid atmospheric environments.