A Highly Connected Metal-Organic Framework with a Specific Nonpolar Nanotrap for Inverse Ethane/ethylene Separation

Efficient separation of ethylene (C2H4) from ethane (C2H6) via a one-step adsorption process is desirable yet challenging. In this work, we report a C2H6-selective polynuclear Tb-MOF [Tb-9(mu(3)-O)2(mu(3)-OH)(12)(H2O)(9)(TCPE)(3)](-)center dot [H3O](+)center dot (solvents)x (TCPE = tetrakis(4-carboxyphenyl)ethylene acid), NKU-200-Tb, assembled via the reticular chemistry principle. The resulting (4,12)-connected framework critically features a high density of nonpolar aromatic rings on the pore surface and forms a specific nanotrap for C2H6 with multiple C-H...pi interaction sites. As a result, NKU-200-Tb exhibits an inverse adsorption behavior with a high C2H6/C2H4 selectivity of 2.06 and a large uptake ratio of 151% (60.27/39.95 cm(3) g(-1)) at 298 K and 1 bar. The superior adsorption properties of NKU-200-Tb, combined with great structural stability, place it among the most promising stable C2H6-selective MOFs. Dynamic breakthrough experiments demonstrate that polymer-grade C2H4 (>99.9%) can be harvested in one step from a binary mixture of C2H6/C2H4 (10/90, v/v). This work signifies the synergy of pore surface chemistry and space confinement in promoting the challenging C2H6/C(2)H(4 )separation.