A quad-core Zn (II) cluster-based microporous metal-organic framework with nonpolar cages for efficient removal of ethane from ethane/ethylene mixtures

Ethane (C 2 H 6 ) and ethylene (C 2 H 4 ) have similar physical and chemical properties, which are critical and difficult for the separation of C 2 H 6 /C 2 H 4 mixtures in the petrochemical process. Traditional C 2 H 4 -selective adsorbents can separate the C 2 H 6 /C 2 H 4 mixtures, but need further desorption treatment to obtain pure C 2 H 4 production. On the contrary, high-pure C 2 H 4 can be prepared in one step by C 2 H 6 -selective porous material. Herein, we present a caged metal-organic framework ( GNU-2 ) based on Zn (II) clusters, which has advantageous adsorption sites and cavity pockets for the reverse capture of C 2 H 6 from C 2 H 6 /C 2 H 4 mixtures. At 298 K and 1 bar, high C 2 H 6 uptake (5.10 mmol g −1 ) and C 2 H 6 /C 2 H 4 selectivity (1.849) were attained based on the activated GNU-2 ( GNU-2a ), exceeding a number of top C 2 H 6 -selective adsorbents. Grand canonical Monte Carlo (GCMC) simulations exhibit that the appropriate chemical environment of nonpolar cage in GNU-2a allows it to continuously maintain closer van der Waals contacts between C 2 H 6 molecule, saturated Zn cluster and nonpolar pore surface through multiple C H···O hydrogen interactions and C H···π hydrogen interactions. Moreover, dynamic breakthrough studies also show that GNU-2a displays the actual separation performances of C 2 H 6 .