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

The separation of C 2 H 2 /CO 2 is an essential but challenging process owing to their similar molecular sizes and physical properties. However, it is noteworthy that these two molecules usually exhibit different orientations in the pore channel. Herein, we report an adsorption site selective occupation strategy by taking advantage of differences in orientation to sieving the C 2 H 2 from CO 2 in a judiciously designed amine-functionalized metal-organic framework, termed as CPL-1-NH 2 . In this material, the incorporation of amino groups not only occupies the adsorption sites of CO 2 molecules and shields the interaction of uncoordinated oxygen atom and CO 2 molecules resulting in a negligible adsorption amount and a decrease in enthalpy of adsorption but also strengthened the binding affinity toward C 2 H 2 molecules. This material thus shows an extremely high amount of C 2 H 2 at low pressure and a remarkable high C 2 H 2 /CO 2 IAST selectivity (119) at 1 bar and 298 K. The experimental breakthrough studies show complete separation of C 2 H 2 from C 2 H 2 /CO 2 mixtures，further confirmed this adsorption site selective occupation strategy promising and practicability.