Design of Adsorption‒Diffusion Dual-Driven MOF Membranes for Efficient CO₂ Separation

Metal-organic frameworks (MOFs) offer exceptional tunability in pore structure and functionality, holding considerable potential for advanced gas separation membranes. However, their advancement is restricted by the permeability-selectivity trade-off and inefficient empirical screening. Herein, we propose an adsorption-diffusion dual-driven design strategy balancing moderate CO₂ adsorption affinity (1 < α_ads,HTCS < 10) and high CO₂ diffusivity selectivity (α_diff,HTCS > 10) within a pore-limiting diameter range of 3.8-4.4 Å. This rationale is corroborated by high-throughput computational screening and experimental membrane performance. Three yfm-topology MOF membranes-CAU-10H, CAU-10pydc, and KMF-1 with finely tuned pore microenvironments were synthesized, with the former two meeting the proposed criteria and KMF-1 serving as a counterexample. As anticipated, CAU-10H and CAU-10pydc exceed the 2019 upper bound for CO₂/CH₄ separation, with CAU-10pydc exhibiting a remarkable CO₂ permeability of ∼2847 Barrer and a selectivity of 185, outperforming most state-of-the-art membranes. Moreover, despite sharing the same kinetic diameter as CO₂, C₂H₂ exhibits 1.5 times higher adsorption affinity, resulting in a significantly lower permeability of only 39 Barrer under the same conditions. These results confirm the adsorption-diffusion dual-driven design principle, providing both theoretical insight and practical guidance for other challenging gas separation scenarios.