Dual-interfacial design of mixed matrix membranes using NH2-UiO-66 MOF and choline chloride/urea DES for enhanced gas separation

The long-standing permeability–selectivity trade-off in polymeric membranes continues to limit the deployment of energy-efficient CO₂ separation technologies. Here, we report a dual-interfacial design strategy that integrates deep eutectic solvents (DESs) with metal organic frameworks (MOFs) to overcome this constraint. A choline chloride-urea DES (1:2) was rationally engineered as a multifunctional compatibilizer and CO₂-affinitive interphase, enabling strong hydrogen-bonding interactions with both Pebax 1657 and UiO-66-type fillers. DES impregnation into UiO-66 and NH₂-UiO-66 preserved crystalline integrity while introducing additional sorption sites and improving polymer–filler adhesion. The resulting mixed matrix membranes (MMMs) exhibit increase in CO₂ permeability by up to ~90 % relative to pristine Pebax while maintaining selectivity, reaching CO₂/CH₄ = 40 and CO₂/N₂ = 62 for NH₂-UiO-66/DES membranes. The membranes show stable mixed-gas performance, reduced activation energies for CO₂ transport, and robust operation across temperature and feed-composition variations. Benchmarking against recent Pebax-based MMMs and Robeson's upper bound confirms that these DES-MOF hybrids not only bridge but surpass the conventional trade-off, matching or outperforming top-reported systems while using environmentally benign, low-cost DESs instead of ionic liquids.