A strongly hydrophobic ethane-selective metal-organic framework for efficient ethane/ethylene separation

The removal of ethane (C2H6) from ethylene (C2H4) is of great importance to afford polymer-grade C2H4 with purity greater than 99.95% as feedstock to produce polyethylene. Adsorptive separation with C2H6-selective metal-organic frameworks (MOFs) can directly produce high-purity C2H4, which has shown bright prospects for replacing the energy-intensive cryogenic distillation. Herein, we demonstrate a robust zirconium MOF possessing hydrophobic pores and oxygen-rich groups, namely MOF-841, can preferentially adsorb C2H6 over C2H4. Experimental adsorption isotherms and breakthrough show high separation performance for the gas mixture of C2H6 and C2H4 due to ultrahigh C2H6 uptake capacity (4.7 mmol/g) and distinctive C2H6/C2H4 uptake ratio (1.35) of MOF-841 at 298 K and 100 kPa. Computational studies reveal that aromatic rings and carboxylate oxygen atoms pointing towards the pore ascribed to trapping C2H6 through synergistic effects arising from multiple van der Waals interactions including C-H∙∙∙π and C-H···O, which are more potent than C2H4-framework interactions.