Separating Saturated Alkylaromatics from Their Unsaturated Analogues Using Metal-Organic Frameworks

This work studies the liquid phase separation of styrene and ethylbenzene on the metal-organic framework [Cu-3(BTC)(2)] (BTC = 1,3,5-benzenetricarboxylate) as well as the analogous separation of vinyltoluenes from ethyltoluenes. Batch and column experiments have been performed to demonstrate the capacity of the material to separate styrene and ethylbenzene. Adsorption capacities of around 20 wt % are measured, while separation factors reach values as high as 5.5. As is demonstrated by UV-vis absorption measurements, the adsorption mechanism is based on specific interactions between the free Cu2+ ligation sites of the framework and the pi-electrons of the aromatic compounds. For the separation of the vinyltoluenes and ethyltoluenes, similar capacities and separation factors have been obtained as for the separation of styrene and ethylbenzene, which suggests an analogous adsorption mechanism.