Efficient separation of xylene isomers by nonporous adaptive crystals of hybrid[3]arene in both vapor and liquid phases

The separation of xylene isomers is a major challenge in the petrochemical industry. However, the traditional distillation method is an energy-intensive process for the separation of xylene isomers. Herein, we develop nonporous adaptive crystals based on hybrid[3]arene H ( Hα ) for the efficient separation of xylene isomers. Hα shows high selectivity for ortho -xylene from the mixture of xylene isomers in both vapor and liquid phases, with a purity of 90.22% and 99.48%, respectively. The single crystal structure analysis suggests that the selectivity is derived from multiple C-H O and C-H π interactions between H and the preferred guest molecule, ortho -xylene, which is also confirmed by visual study of weak intermolecular interactions and electrostatic potential maps between H and xylene isomers. Besides, the Gibbs free energies of Hα for xylene isomers show that the adsorption energy of Hα for ortho -xylene is lower than that of meta -xylene or para -xylene, further confirming the preferred adsorption of Hα for ortho -xylene. Moreover, Hα is highly recyclable due to the reversible transformation between guest-free and guest-contained structures. This work will afford a new strategy for the separation of other important aromatic isomers and provide inspiration for the use of supramolecular host-based nonporous adaptive crystals in other energy-intensive separation methods. An efficient strategy for separation of xylene isomers in both vapor and liquid phases based on nonporous adaptive crystals of hybrid[3]arene is developed, showing good performance and high recyclability for separation of o -xylene, providing a new method for separation of xylene isomers.