Cross‐Linking CdSO4‐Type Nets with Hexafluorosilicate Anions to Form an Ultramicroporous Material for Efficient C2H2/CO2 and C2H2/C2H4 Separation

Abstract A 4 4 .6 10 .8 topology hybrid ultramicroporous material (HUM), {[Cu 1.5 F(SiF 6 )(L) 2.5 ]·G} n , (L = 4,4′‐bisimidazolylbiphenyl, G = guest molecules), 1 , formed by cross‐linking interpenetrated 3D four‐connected CdSO 4 ‐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 6 2− 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 C 2 H 2 over CO 2 and C 2 H 4 by hydrogen bonding interactions with a high C 2 H 2 isosteric heat of adsorption ( Q st ) of ≈42.3 kJ mol −1 at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for C 2 H 2 /CO 2 and C 2 H 2 /C 2 H 4 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 C 2 H 2 /CO 2 mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of C 2 H 2 stems from the chelating fix of C 2 H 2 between SiF 6 2− anion and coordinated F − anion.