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

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 C₂H₂/CO₂ separation properties. The C₂H₂ 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 CO₂ uptakes under the same conditions. The C₂H₂/CO₂ 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 C₂H₂/CO₂ separation with a large C₂H₂ 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 C₂H₂, which collaboratively enhance framework-C₂H₂ interactions as revealed by computional simulations.