Efficient Ethylene/Ethane Separation Achieved by a Temperature-Responsive Flexible MOF

This study investigates the temperature-responsive thermodynamic behavior of a zinc-based flexible metal-organic framework for ethylene/ethane C₂H₄/C₂H₆ separation. Isothermal adsorption suggested a highly sensitive, temperature-dependent guest-induced structural transition. At 273 K, C₂H₄ triggers a pronounced gate-opening effect at low pressures with a broad desorption hysteresis loop, while C₂H₆ shows only a marginal stepwise uptake increase at about 0.6 bar. Crucially, elevating the temperature to 298 K shifts the C₂H₄ transition threshold to higher pressures and completely suppresses the C₂H₆ response. This divergence enables the selective triggering of the framework expansion exclusively by C₂H₄ at room temperature. Further heating to 323 K entirely suppresses phase-transition characteristics for both gases. Dynamic mixed-gas breakthrough experiments confirm that precise thermal regulation strikes an optimal balance, achieving maximized fixed-bed separation selectivity while preserving a substantial capacity. This work demonstrates temperature as a key parameter to tailor the dynamic separation performance of flexible adsorbents in practical PSA/TSA applications.