Optimizing Multivariate Metal–Organic Frameworks for Efficient C₂H₂/CO₂ Separation

Adsorptive separation of acetylene (C₂H₂) from carbon dioxide (CO₂) promises a practical way to produce high-purity C₂H₂ required for industrial applications. However, challenges exist in the pore environment engineering of porous materials to recognize two molecules due to their similar molecular sizes and physical properties. Herein, we report a strategy to optimize pore environments of multivariate metal-organic frameworks (MOFs) for efficient C₂H₂/CO₂ separation by tuning metal components, functionalized linkers, and terminal ligands. The optimized material UPC-200(Al)-F-BIM, constructed from Al³⁺ clusters, fluorine-functionalized organic linkers, and benzimidazole terminal ligands, demonstrated the highest separation efficiency (C₂H₂/CO₂ uptake ratio of 2.6) and highest C₂H₂ productivity among UPC-200 systems. Experimental and computational studies revealed the contribution of small pore size and polar functional groups on the C₂H₂/CO₂ selectivity and indicated the practical C₂H₂/CO₂ separation of UPC-200(Al)-F-BIM.