Cross-Linking CdSO-Type Nets with Hexafluorosilicate Anions to Form an Ultramicroporous Material for Efficient CH/CO and CH/CH Separation.

A 4.6.8 topology hybrid ultramicroporous material (HUM), {[CuF(SiF)(L)]·G}, (L = 4,4'-bisimidazolylbiphenyl, G = guest molecules), 1, formed by cross-linking interpenetrated 3D four-connected CdSO-type nets with hexafluorosilicate anions is synthesized and evaluated in the context of gas sorption and separation herein. 1 is the first HUM functionalized with two different types of fluorinated sites (SiF and F anions) lining along the pore surface. The optimal pore size (≈5 Å) combining mixed and high-density electronegative fluorinated sites enable 1 to preferentially adsorb CH over CO and CH by hydrogen bonding interactions with a high CH isosteric heat of adsorption (Q) of ≈42.3 kJ mol at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for CH/CO and CH/CH that surpasses many well-known sorbents. Dynamic breakthrough experiments are conducted to confirm the practical separation capability of 1, which reveal an impressive separation factor of 6.1 for equimolar CH/CO mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of CH stems from the chelating fix of CH between SiF anion and coordinated F anion.