Journal of the American Chemical Society, Vol.142, No.5, 2222-2227, 2020
Pore-Space-Partition-Enabled Exceptional Ethane Uptake and Ethane-Selective Ethane-Ethylene Separation
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 cm(3)/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 cm(3)/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 degrees C) and aqueous stability, low regeneration energy, and a high degree of chemical and geometrical tunability within the same isoreticular framework.