A new SIFSIX anion pillared cage MOF with crs topological structure for efficient C2H2/CO2 separation

Due to the similar physicochemical properties of acetylene (C2H2) and carbon dioxide (CO2), separating C2H2 from a CO2/C2H2 mixture poses a significant challenge in the petrochemical industry. Herein, we successfully synthesized a novel SiF62- anion pillared cage metal-organic framework ZNU-15 possessing a new crs topological structure for the selective capture of C2H2. As a linear bidentate linker, the fluorinated SiF62- anion partitions the pores into various sized cages. ZNU-15 displays moderate adsorption for C2H2 with a capacity of 36.0 cm3 g-1 at 298 K and 1 bar, which is 2.7 times higher than the CO2 uptake. The IAST selectivity of C2H2/CO2 for ZNU-15 at 298 K and 100 kPa is 10.5, surpassing that of most reported materials. The Qst values for C2H2 and CO2 at zero coverage are 54.0 and 42.8 kJ mol-1, respectively. Moreover, breakthrough experimental tests show that ZNU-15 is capable of effectively separating C2H2 from a C2H2/CO2 mixture. Theoretical calculations further indicate that C2H2 is preferentially trapped by the small cage with four cooperative hydrogen bonds.