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 cm(3) g(-1)), meanwhile the CO2 uptake reduces to 14.1 cm(3) g(-1), only 17.4% of that on SOFOUR-1-Zn (81.0 cm(3) 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 cm(3) g(-1) C2H2 of 99.5% purity or 33.2 cm(3) 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 cm(3) 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.

Automated summary

In this study, a novel sulfate-pillared MOF adsorbent (SOFOUR-TEPE-Zn) using the TEPE ligand with dense electronegative pore surfaces is reported for acetylene/carbon dioxide (C2H2/CO2) separation. Compared to the prototype SOFOUR-1-Zn, SOFOUR-TEPE-Zn shows a higher C2H2 uptake and reduced CO2 uptake, leading to a high C2H2/CO2 selectivity. Dynamic breakthrough experiments confirm its application feasibility and good cyclability at various flow rates. The pressure swing adsorption processes reveal a high gas recovery rate and production of high purity C2H2.