Effect of Orbital-Symmetry Matching in a Metal-Organic Framework for Highly Efficient C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 Separations.

The detailed mechanism of metal-organic-framework (MOF)-based separation materials is still obscure, which obviously hinders their actual application. To address this problem, a trinuclear Cu-cluster-based MOF with a minimum metal-active plane was synthesized for the study of the very challenging C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 separations. Via dispersion-corrected density functional theory calculations, it is indicated that the difference of the adsorption energy accounts for the excellent separation properties toward C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 mixtures, while the frontier molecular orbitals demonstrate that the adsorption-energy difference originates from the orbital-symmetry difference of gas molecules. All of these results provide not only deep insight into the separation mechanism but also an alternative strategy to prepare efficient adsorbents.