Pore-Space-Partition-Enabled Exceptional Ethane Uptake and Ethane-Selective Ethane–Ethylene Separation
Huajun Yang, Yanxiang Wang, Rajamani Krishna, Xiaoxia Jia, Yong Wang, Anh N. Hong, Candy Dang, Henry E. Castillo, Xianhui Bu, Pingyun Feng
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.