Ultramicroporous Metal-Organic Framework with Inert Pore Surfaces for Inversed Separation of Ethylene from C2 Hydrocarbons Mixtures.

The achievement of direct C2H4 separation from C2 hydrocarbons is very challenging in the petrochemical industry due to their similar molecular sizes, boiling points, and physicochemical properties. In this work, a nonpolar/inert ultramicroporous metal-organic framework (MOF), [Co3(µ3-OH)(tipa)(bpy)1.5]·3DMF·6H2O (1), with stand-alone one-dimensional square tubular channels was successfully constructed, its pore enriched with plenty of aromatic rings causing nonpolar/inert pore surfaces. The MOF shows preferential adsorption of C2H6 compared to C2H4 and C2H2 in the low-pressure region, which is further verified by adsorption heats and selectivities. The C2H4 separation potential in one step for binary C2H6/C2H4 (50/50 and 10/90) and ternary C2H4/C2H6/C2H2 (89/10/1) is also examined by transient breakthrough simulations. Moreover, grand canonical Monte Carlo simulations demonstrate that the unique reversed adsorption mechanism is due to the shortest and most number of C-H···π interactions between C2H6 and the framework.