Hydrophobic PDMS overlayer on wood-supported Mg-MOF-74 enables durable CO2 capture under humid flue gas

Metal–organic frameworks often lose CO 2 capacity in hot, humid flue gas because H 2 O competes for open metal sites (OMSs). Here we report a dual-stabilized, wood-based adsorbent in which Mg-MOF-74 is grown on an aminated wood sponge and overcoated with an ultrathin polydimethylsiloxane (PDMS) layer, coupling support immobilization with interfacial hydrophobization while preserving access to OMSs. Under flue-gas-relevant conditions (323 K, 50% RH), the material delivers a CO 2 uptake of 1.68 mmol·g −1 (≈89% of its dry-state capacity) and an IAST CO 2 /N 2 selectivity of 144 for a 50/50 mixture at 323 K. Humid-gas breakthrough tests confirm robust separation performance. Density functional theory (DFT) calculations attribute the humidity tolerance and selectivity to the synergy between accessible OMSs and PDMS-mediated interfacial polarity, without increasing the isosteric heat of adsorption, thereby enabling energy-efficient regeneration. The framework retains its crystallinity after 30 days of water immersion, and a techno-economic estimate projects a material cost of approximately US$10.36 kg −1 at a 1000 t·yr −1 scale. This scalable architecture reconciles capacity, selectivity, humidity resistance, and cost for post-combustion CO 2 capture.