Effect of Orbital-Symmetry Matching in a Metal–Organic Framework for Highly Efficient C2H2/C2H4 and C2H2/CO2 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 C2H2/C2H4 and C2H2/CO2 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 C2H2/C2H4 and C2H2/CO2 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.