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.