Reversed C2H6/C2H4 separation in interpenetrated diamondoid coordination networks with enhanced host–guest interaction

The separation of ethane (C2H6) from ethylene (C2H4) is one of the most challenging and important tasks in chemical industry. Herein we report two interpenetrated diamondoid (dia) coordination networks, Dia-4-M [M(pba)2] (pba = 4-(4-pyridyl)benzoate); M = Ni or Co), that can directly capture ethane from ethane-ethylene mixtures with reverse C2H6/C2H4 separation. Both materials not only exhibit ultra-high C2H6 uptake (100 cm3 g−1 for Dia-4-Ni; 103 cm3 g−1 for Dia-4-Co) but also display good C2H6/C2H4 selectivity (1.76 for Dia-4-Ni; 2.04 for Dia-4-Co). Such C2H6/C2H4 separation performance was confirmed by dynamic breakthrough experiments. Dia-4-M could extract low concentrated of C2H6 from C2H6/C2H4 mixture (v(C2H6)/v(C2H4) = 1:9 and 1:15) and produce high purity (99.9%) of C2H4 under ambient conditions. The mechanism for selective C2H6/C2H4 separation was clarified through Grand Canonical Monte Carlo (GCMC) simulations and Density functional theory (DFT) calculations. Overall, this research demonstrates that Dia-4-M has a significant potential as effective C2H6-selective adsorbents for the purification of ethylene in practice.