Adsorption in Reversed Order of C 2 Hydrocarbons on an Ultramicroporous Fluorinated Metal-Organic Framework.

Metal-organic frameworks have been widely studied in the separation of C hydrocarbons, which usually preferentially bind unsaturated hydrocarbons with the order of acetylene (C H )>ethylene (C H )>ethane (C H ). Herein, we report an ultramicroporous fluorinated metal-organic framework Zn-FBA (H FBA=4,4'-(hexafluoroisopropylidene)bis(benzoic acid)), shows a reversed adsorption order characteristic for C hydrocarbons, that the uptake for C hydrocarbons of the framework and the binding affinity between the guest molecule and the framework follows the order C H >C H >C H . Density-functional theory calculations confirm that the completely reversed adsorption order behavior is attributed to the close van der Waals interactions and multiple cooperative C-H⋅⋅⋅F hydrogen bonds between the framework and C H . Moreover, Zn-FBA exhibits a high selectivity of about 2.9 for C H over C H at 298 K and 1 bar. The experimental breakthrough studies show that the high-purity C H can be obtained from C H and C H mixtures in one step.