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 2 hydrocarbons, which usually preferentially bind unsaturated hydrocarbons with the order of acetylene (C 2 H 2 )>ethylene (C 2 H 4 )>ethane (C 2 H 6 ). Herein, we report an ultramicroporous fluorinated metal-organic framework Zn-FBA (H 2 FBA=4,4'-(hexafluoroisopropylidene)bis(benzoic acid)), shows a reversed adsorption order characteristic for C 2 hydrocarbons, that the uptake for C 2 hydrocarbons of the framework and the binding affinity between the guest molecule and the framework follows the order C 2 H 6 >C 2 H 4 >C 2 H 2 . 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 2 H 6 . Moreover, Zn-FBA exhibits a high selectivity of about 2.9 for C 2 H 6 over C 2 H 4 at 298 K and 1 bar. The experimental breakthrough studies show that the high-purity C 2 H 4 can be obtained from C 2 H 6 and C 2 H 4 mixtures in one step.