Ethane-selective metal-organic frameworks for one-step purification of ethylene

Ethylene/ethane separations remain among the most energy-intensive operations in the petrochemical value chain, owing to their close molecular sizes, polarizabilities, and volatilities. While cryogenic distillation is industrially entrenched, adsorption-based processes promise substantial energy savings and simpler flowsheets, particularly when impurity-targeted adsorbents are employed. This comprehensive review systematically examines recent advancements in ethane-selective MOF adsorbents that enable one-step purification of polymer-grade ethylene directly from cracked-gas mixtures. We delineate three fundamental separation mechanisms that govern selective ethane capture: (i) strategic incorporation of electronegative binding sites for enhanced C-H⋯site interactions, (ii) engineering of low-polarity hydrophobic pore environments to leverage different van der Waals interactions, and (iii) utilization of framework flexibility and gate-opening phenomena that preferentially accommodate ethane molecules. This review critically evaluates representative MOF systems across key performance metrics including equilibrium uptake capacities, IAST-predicted selectivity values, and experimental breakthrough behaviors under mixed-gas conditions. By establishing clear structure-property relationships and identifying emerging design principles, this work provides valuable insights for the rational development of next-generation ethane-selective adsorbents with optimized separation performance.