High Ethene/Ethane Selectivity in 2,2′-Bipyridine-Based Silver(I) Complexes by Removal of Coordinated Solvent

Following removal of coordinated CH3CN, the resulting complexes [Ag-I(2,2'-bipyridine)][BF4] (I) and [Ag-I(6,6'-dimethyl-2,2'-bipyridine)][OTf] (2) show ethene/ethane sorption selectivities of 390 and 340, respectively, and corresponding ethene sorption capacities of 2.38 and 2.18 mmol g(-1) when tested at an applied gas pressure of 90 kPa and a temperature of (20 +/- 1) degrees C. These ethene/ethane selectivities are 13 times higher than those reported for known solid sorbents for ethene/ethane separation. For 2, ethene sorption reached 90% of equilibrium capacity within 15 minutes, and this equilibrium capacity was maintained over the three sorption/desorption cycles tested. The rates of ethene sorption were also measured. To our knowledge, these are the first complexes, designed for olefin/paraffin separations, which have open silver(I) sites. The high selectivities arise from these open silver(I) sites and the relatively low molecular surface areas of the complexes.