Kinetic separation of C2H6/C2H4 in a cage-interconnected metal–organic framework: an interaction-screening mechanism

Abstract

Kinetic-based adsorptive separation is deemed as an energy-efficient approach for gas purification, yet its underlying mechanism is difficult to justify. Herein, we propose an intriguing interaction-screening mechanism with a cage-interconnected metal–organic framework (JNU-2) as a model via a multi-scale theoretical approach. Grand Canonical Monte Carlo (GCMC) simulations establish gas diffusion channels with the calculated C₂H₄ and C₂H₆ adsorptions comparable to the experimental ones. Molecular dynamic (MD) simulations reveal single-molecule passages along the diffusion channel and that the probability of C₂H₆ diffusing into the passage is nine times higher than that of C₂H₄. Density functional theory (DFT) calculations further confirm an overall preferential interaction with C₂H₆ passing through the single-molecule passage. This work has successfully demonstrated a theoretical methodology of multi-scale simulations and depicted a rarely observed interaction-screening mechanism in JNU-2 that corroborates its balanced adsorption capacity and C₂H₆/C₂H₄ adsorption selectivity. Such a methodology should be applicable to other well-defined structures for a better understanding of their gas adsorption/separation behaviours.