Engineering Pore Environments of Sulfate-Pillared Metal-Organic Framework for Efficient C₂H₂/CO₂ Separation with Record Selectivity

Engineering pore environments exhibit great potential in improving gas adsorption and separation performances but require specific means for acetylene/carbon dioxide (C₂H₂/CO₂) separation due to their identical dynamic diameters and similar properties. Herein, a novel sulfate-pillared MOF adsorbent (SOFOUR-TEPE-Zn) using 1,1,2,2-tetra(pyridin-4-yl) ethene (TEPE) ligand with dense electronegative pore surfaces is reported. Compared to the prototype SOFOUR-1-Zn, SOFOUR-TEPE-Zn exhibits a higher C₂H₂ uptake (89.1 cm³ g⁻¹), meanwhile the CO₂ uptake reduces to 14.1 cm³ g⁻¹, only 17.4% of that on SOFOUR-1-Zn (81.0 cm³ g⁻¹). The high affinity toward C₂H₂ than CO₂ is demonstrated by the benchmark C₂H₂/CO₂ selectivity (16 833). Furthermore, dynamic breakthrough experiments confirm its application feasibility and good cyclability at various flow rates. During the desorption cycle, 60.1 cm³ g⁻¹ C₂H₂ of 99.5% purity or 33.2 cm³ g⁻¹ C₂H₂ of 99.99% purity can be recovered by stepped purging and mild heating. The simulated pressure swing adsorption processes reveal that 75.5 cm³ g⁻¹ C₂H₂ of 99.5+% purity with a high gas recovery of 99.82% can be produced in a counter-current blowdown process. Modeling studies disclose four favorable adsorption sites and dense packing for C₂H₂.