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]n, BTB3- = benzene-1,3,5-tribenzoate and BPY = 4,4'-bipyridine) and its fluorinated JXNU-15(F) ([Co6(μ3-OH)6(SFBTB)2(BPY)3]n) based on the fluorous 1,3,5-tri(3,5-bifluoro-4-carboxyphenyl)benzene (SFBTB3-) 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.