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 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.