Fluorido-bridged robust metal-organic frameworks for efficient C₂H₂/CO₂ separation under moist conditions

The modern technology for acetylene production is inevitably accompanied by the contamination of carbon dioxide and moisture impurities. Metal-organic frameworks (MOFs), with rational configurations of fluorine as the hydrogen-bonding acceptor (HBA), exhibit excellent affinities to capture acetylene from the gas mixtures. Currently, most research studies feature anionic fluorine groups as structural pillars (e.g., SiF₆²⁻, TiF₆²⁻, NbOF₅²⁻), whereas in situ insertion of fluorine into metal clusters is rather challenging. Herein, we report a unique fluorine-bridged Fe-MOF, i.e., DNL-9(Fe), which is assembled by mixed-valence Fe^IIFe^III clusters and renewable organic ligands. The fluorine species in the coordination-saturated structure offer superior C₂H₂-favored adsorption sites facilitated by hydrogen bonding, with a lower C₂H₂ adsorption enthalpy than other reported HBA-MOFs, demonstrated by static/dynamic adsorption tests and theoretical calculations. Importantly, DNL-9(Fe) shows exceptional hydrochemical stability under aqueous, acidic, and basic conditions, and its intriguing performance for C₂H₂/CO₂ separation was even maintained at a high relative humidity of 90%.