Collaborative pore partition and pore surface fluorination within a metal–organic framework for high-performance C2H2/CO2 separation

Abstract

• The C 2 H 2 /CO 2 separation for fluorinated and nonfluorinated MOFs is presented. • JXNU-12(F) exhibits significantly enhanced C 2 H 2 /CO 2 separation than that of JXNU-12. • JXNU-12(F) dispalys aprominent C 2 H 2 -captured amount in the breakthrough experiments. • Fluorination exerts a pronounced impact on C 2 H 2 uptake and C 2 H 2 /CO 2 selectivity. • The pores induced by pore partition and fluorination are optimized for trapping C 2 H 2 . Inspired by the unique properties of fluorous compounds, the deliberate replacement of H atoms with F atoms in organic linkers of metal–organic frameworks (MOFs) could be of highly interesting. Herein we rationally developed a fluorinated MOF of JXNU-12(F) derived from the parent MOF of JXNU-12 in the presence of the pore partition agent. Remarkably, H/F substitution maintains the crystal structures of MOFs but dramatically enhances the C 2 H 2 /CO 2 separation properties. The C 2 H 2 uptake of JXNU-12(F) (298 K and 1 bar) is 1.48 times higher than that of JXNU-12 even though the pore volume of JXNU-12(F) is 84% of JXNU-12. Whereas both MOFs exhibit the same CO 2 uptakes under the same conditions. The C 2 H 2 /CO 2 adsorption selectivity of JXNU-12(F) at 1 bar and 298 K is 2 times that of JXNU-12, emphasizing the importance of fluorine substitution. An excellent C 2 H 2 /CO 2 separation with a large C 2 H 2 captured amount of 4.7 mmol g −1 was achieved with JXNU-12(F), ranking among the best-performing MOFs. The significant performance enhancement in JXNU-12(F) is rationalized by the large electronegativity and polarizability of fluorine groups exposed on the pore surfaces and the well-matched pore spaces generated by pore partition for trapping C 2 H 2 , which collaboratively enhance framework-C 2 H 2 interactions as revealed by computional simulations.