Microregulation of Pore Channels in Covalent-Organic Frameworks Used for the Selective and Efficient Separation of Ethane

The removal of low content of ethane (C2H6) from ethylene (C2H4) using C2H6-selective adsorbents to reduce the energy consumption in the petrochemical industry is one of the meaningful and challenging tasks in separation research. Herein, we report for the first time the systematic research of covalent-organic frameworks (COFs) as a platform used for the separation of light hydrocarbons based on their specific topology. Benefiting from its richly distributed weakly polar surface and suitable pore cavities, COF-1 exhibits the highest adsorption selectivity (1.92 at 298 K and 1 bar) for the C2H6/C2H4 mixture among the COFs studied. Density functional theory calculations clearly revealed that COF-1 can exhibit multiple C-H center dot center dot center dot pi interactions with ethane in its suitable pore environment and thus preferentially binds to ethane over ethylene. Finally, breakthrough experiments proved that COF-1 may be regarded as an effective porous adsorbent with polymergrade C2H4 obtained directly from C2H6/C2H4 mixtures at 298 K and 1 bar.