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

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.