Can Metal-Organic Framework Separate 1-Butene from Butene Isomers?

The separation of 1-butene from the other isomers is an industrially important but challenging task because these isomers mainly differ only by the position of C=C double bond with many of their physical properties very similar. In this work, we propose using first-principles calculations that Fe-MOF-74 can be a promising candidate for the separation of 1-butene from all other isomers with high selectivity. We demonstrate that the underlying mechanism of this olefin separation is the steric interactions; that is, 1-butene with terminal double bond has the smallest steric interactions with the framework and therefore can approach the metal binding sites more closely for stronger pi-complexation. This combined effect (pi-complexation modulated by steric interactions) in MOFs with open metal sites can offer a promising design strategy for difficult separation of even longer olefin isomers by properly engineering the lengths and functional groups of the MOF linkers.