Stepwise pillar-ligand fluorination strategy within interpenetrated metal-organic frameworks for efficient C2H2/CO2 separation

The efficient separation of C2H2/CO2 possesses great commercial and research value and remains challenging due to their similar molecular sizes and physical properties. Functionalization is a powerful strategy for precisely regulating the pore environment of porous adsorbents, notably metal-organic frameworks (MOFs), for recognizing target molecules. Here, we construct three interpenetrated MOFs using a stepwise fluorinated pillar-ligand strategy. Interestingly, the degree of interpenetration can be managed by introducing different pillars. The unique interpenetrating structure cooperates with fluorine-rich pore environment significantly improves the C2H2 uptake and the C2H2/CO2 separation selectivity. The optimized difluorine-functionalized UPC-193 exhibits the highest C2H2 adsorption capacity (80.45 cm3/g) and separation efficiency (C2H2/CO2 uptake ratio of 1.9) among UPC-190 systems at ambient conditions. Ideal adsorbed solution theory (IAST) calculations, molecular modeling studies, and breakthrough experiments comprehensively demonstrate that UPC-193 is an effective MOF adsorbent for equimolar C2H2/CO2 separation. The stepwise pillar-ligand fluorination strategy proves to be an effective approach to extend the functionality of MOFs for challenging gas separations.