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.