A flexible metal–organic framework with adaptive pores for high column-capacity gas chromatographic separation

Abstract

Solvothermal reaction of Zn(NO₃)₂ and a bifunctional ligand 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid (H₂mpba) using benzene as template gave a two-fold interpenetrated porous framework [Zn₂(Hmpba)₂(mpba)]·2C₆H₆ (1·C₆H₆ or MCF-54), which displayed single-crystal to single-crystal (SCSC) structural transformations upon activation and adsorption of methanol, toluene and cyclohexane. Single-crystal structural analysis and computational simulations demonstrated that compound 1 possesses adaptive pores toward various shapes or arrangements of guests. Using silicone rubber as binder, microcrystalline powders of 1 were coated on the inner surface of a capillary column for gas chromatography, which displayed high separation performances and/or abnormal separation sequences for similar benzene homologues. By virtue of the large loading amount of adsorbent, the column shows extra-large column-capacity, being almost 300 times larger than that of common commercial capillary columns, leading to good selectivities and resolutions even in the presence of large amount of interferents.