Boosting the C₂H₂/CO₂ Separation Performance of Metal-Organic Frameworks through Fluorine Substitution

A pair of metal-organic frameworks (MOFs) of JXNU-15 (formulated as [Co₆(μ₃-OH)₆(BTB)₂(BPY)₃], BTB^3- = benzene-1,3,5-tribenzoate and BPY = 4,4'-bipyridine) and its fluorinated JXNU-15(F) ([Co₆(μ₃-OH)₆(SFBTB)₂(BPY)₃]) based on the fluorous 1,3,5-tri(3,5-bifluoro-4-carboxyphenyl)benzene (SFBTB^3-) ligands were presented. The detailed comparisons of the acetylene/carbon dioxide (C₂H₂/CO₂) separation abilities between the isostructural JXNU-15(F) and JXNU-15 were presented. In comparison with the parent JXNU-15, the higher C₂H₂ uptake, larger adsorption selectivity of the C₂H₂/CO₂ (50/50) mixture, and enhanced C₂H₂/CO₂ separation performance endow JXNU-15(F) with highly efficient C₂H₂/CO₂ separation performance, which is demonstrated by singe-component gas adsorptions and dynamic gas mixture breakthrough experiments. The fluorine substituents exert the crucial effects on the enhanced C₂H₂/CO₂ separation ability of JXNU-15(F) and play the dominant role in the C₂H₂-framework interactions, as uncovered by computational simulations. This work illustrates a powerful fluorine substitution strategy for boosting C₂H₂/CO₂ separation ability for MOFs.