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.