Fluorido-bridged robust metal–organic frameworks for efficient C(2)H(2)/CO(2) 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., SiF(6)(2−), TiF(6)(2−), NbOF(5)(2−)), 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(II)Fe(III) clusters and renewable organic ligands. The fluorine species in the coordination-saturated structure offer superior C(2)H(2)-favored adsorption sites facilitated by hydrogen bonding, with a lower C(2)H(2) 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 C(2)H(2)/CO(2) separation was even maintained at a high relative humidity of 90%.