Selective Adsorption and Separation of o-Xylene Using an Aluminum-Based Metal-Organic Framework

Separation and purification of C8 aromatics is still a great challenge owing to their similar boiling point and molecular size. Herein, an aluminum-based metal-organic framework was synthesized to investigate the ability of discriminating C8 aromatics. Both the single-component and multicomponent experiments exhibited the preferential adsorption of o-xylene with the adsorption order of o-xylene > p-xylene > m-xylene > ethylbenzene. Especially, the separation selectivity of o-xylene over m-xylene can reach as high as 8.1, which exceeds the reported values using MOFs in the liquid phase. The results of the experiment in combination of calculations revealed that the interaction between polarity groups of frameworks and guests besides the stacking interaction among guest molecules is the main interaction. The cooperative effect of mu-OH groups and the aluminum-metal cluster can strengthen the electrostatic interactions for o-xylene. With the help of density function theory calculations, it is believed that the difference in binding affinities with the framework endows this MOF with excellent selective adsorption and separation of o-xylene from the C8 mixture.