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

The separation of ethane (C 2 H 6 ) from ethylene (C 2 H 4 ) 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 C 2 H 6 /C 2 H 4 separation. Both materials not only exhibit ultra-high C 2 H 6 uptake (100 cm 3 g −1 for Dia-4-Ni ; 103 cm 3 g −1 for Dia-4-Co ) but also display good C 2 H 6 /C 2 H 4 selectivity (1.76 for Dia-4-Ni ; 2.04 for Dia-4-Co ). Such C 2 H 6 /C 2 H 4 separation performance was confirmed by dynamic breakthrough experiments. Dia-4-M could extract low concentrated of C 2 H 6 from C 2 H 6 /C 2 H 4 mixture (v(C 2 H 6 )/v(C 2 H 4 ) = 1:9 and 1:15) and produce high purity (99.9%) of C 2 H 4 under ambient conditions. The mechanism for selective C 2 H 6 /C 2 H 4 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 C 2 H 6 -selective adsorbents for the purification of ethylene in practice.