Pore-Space-Partition-Enabled Exceptional Ethane Uptake and Ethane-Selective Ethane-Ethylene Separation

Abstract

An ideal material for C₂H₆/C₂H₄ separation would simultaneously have the highest C₂H₆ uptake capacity and the highest C₂H₆/C₂H₄ selectivity. But such material is elusive. A benchmark material for ethane-selective C₂H₆/C₂H₄ separation is peroxo-functionalized MOF-74-Fe that exhibits the best known separation performance due to its high C₂H₆/C₂H₄ selectivity (4.4), although its C₂H₆ uptake capacity is moderate (74.3 cm³/g). Here, we report a family of pore-space-partitioned crystalline porous materials (CPMs) with exceptional C₂H₆ uptake capacity and C₂H₆/C₂H₄ separation potential (i.e., C₂H₄ recovered from the mixture) despite their moderate C₂H₆/C₂H₄ selectivity (up to 1.75). The ethane uptake capacity as high as 166.8 cm³/g at 1 atm and 298 K, more than twice that of peroxo-MOF-74-Fe, has been achieved even though the isosteric heat of adsorption (21.9-30.4 kJ/mol) for these CPMs is as low as about one-third of that for peroxo-MOF-74-Fe (66.8 kJ/mol). While the overall C₂H₆/C₂H₄ separation potentials have not yet surpassed peroxo-MOF-74-Fe, these robust CPMs exhibit outstanding properties including high thermal stability (up to 450 °C) and aqueous stability, low regeneration energy, and a high degree of chemical and geometrical tunability within the same isoreticular framework.