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

[Display omitted] •The insertion of pillar ligands of UPC-190 series MOFs can lead to changes in the interpenetrating structure. The degree of interpenetration can be managed by introducing different pillars.•Theoretical calculations demonstrate that the fluorine atom on pillar ligands is an effective interaction site for C2H2 molecules. This means that fluorine atoms can act as active sites that interact with C2H2 molecules, thereby influencing their adsorption behavior.•The formation of interpenetrating structures and the stepwise fluorination strategy gradually improve the IAST selectivity and C2H2 uptake of the sample. This strategy proves guidance for designing MOFs for challenging gas separations. 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.