Boosting the C 2 H 2 /CO 2 Separation Performance of Metal-Organic Frameworks through Fluorine Substitution.

A pair of metal-organic frameworks (MOFs) of JXNU-15 (formulated as [Co 6 (μ 3 -OH) 6 (BTB) 2 (BPY) 3 ] n , BTB 3- = benzene-1,3,5-tribenzoate and BPY = 4,4'-bipyridine) and its fluorinated JXNU-15(F) ([Co 6 (μ 3 -OH) 6 (SFBTB) 2 (BPY) 3 ] n ) 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 (C 2 H 2 /CO 2 ) separation abilities between the isostructural JXNU-15(F) and JXNU-15 were presented. In comparison with the parent JXNU-15, the higher C 2 H 2 uptake, larger adsorption selectivity of the C 2 H 2 /CO 2 (50/50) mixture, and enhanced C 2 H 2 /CO 2 separation performance endow JXNU-15(F) with highly efficient C 2 H 2 /CO 2 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 C 2 H 2 /CO 2 separation ability of JXNU-15(F) and play the dominant role in the C 2 H 2 -framework interactions, as uncovered by computational simulations. This work illustrates a powerful fluorine substitution strategy for boosting C 2 H 2 /CO 2 separation ability for MOFs.