Control of pore structure by the solvent effect for efficient ethane/ethylene separation

The purification of ethylene (C 2 H 4 ) by selective adsorption of small amounts of ethane (C 2 H 6 ) is a crucial industrial process. However, most porous adsorbents prefer C 2 H 4 over C 2 H 6 due to the increase in kinetic diameter and decrease in quadrupole moment from C 2 H 4 to C 2 H 6 . The construction of ethane-selective adsorbents for ethylene purification is therefore a very challenging task. In this study, we designed and synthesized a family of C 2 H 6 -selective metal–organic framework (MOF) adsorbents, named Co-1-ina , Co-5-ina and Co-9-ina , through the strategy of crystal engineering using the same metal salt (Co 2+ ) and ligand (isonicotinic acid). Notably, the pore structures and topologies of these materials vary according to the reaction conditions. Among them, Co-9-ina has the highest C 2 H 6 adsorption capacity and C 2 H 6 /C 2 H 4 separation performance. The C 2 H 6 /C 2 H 4 selectivity of Co-9-ina at 298 K and 1 bar is astoundingly 2.69, which is greater than most C 2 H 6 -selective MOFs reported to date. The pyridine rings bind more strongly to C 2 H 6 via van der Waals interactions for ethane adsorption according to theoretical calculations and single crystal structures. The C 2 H 6 /C 2 H 4 separation performance for Co-9-ina was further validated by breakthrough studies under dynamic conditions.