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.