Adsorption Site Selective Occupation Strategy within a Metal-Organic Framework for Highly Efficient Sieving Acetylene...

The separation of acetylene and carbon dioxide is an essential but challenging process owing to the similar molecular sizes and physical properties of the two gas molecules. Notably, these molecules usually exhibit different orientations in the pore channel. We report an adsorption site selective occupation strategy by taking advantage of differences in orientation to sieve the C₂ H₂ from CO₂ in a judiciously designed amine-functionalized metal-organic framework, termed CPL-1-NH₂ . In this material, the incorporation of amino groups not only occupies the adsorption sites of CO₂ molecules and shields the interaction of uncoordinated oxygen atom and CO₂ molecules resulting in a negligible adsorption amount and a decrease in enthalpy of adsorption but also strengthened the binding affinity toward C₂ H₂ molecules. This material thus shows an extremely high amount of C₂ H₂ at low pressure and a remarkably high C₂ H₂ /CO₂ IAST selectivity (119) at 1 bar and 298 K.