Highly Selective Separation of <i>cis</i> - over <i>trans</i> -1,2-Dimethylcyclohexane Isomers by Nonporous Adaptive Crystals of Pillar[ <i>n</i> ]arenes

The separation of <i>cis</i>-<i>trans</i> isomers is one of the important research fields in chemical industries. In this work, nonporous adaptive crystals (NACs) based on perethylated pillar[<i>n</i>]arenes were used for the adsorption and separation of <i>cis</i>- and <i>trans</i>-1,2-dimethylcyclohexane (<i>cis</i>-<b>G</b> and <i>trans</i>-<b>G</b>). NACs of perethylated pillar[5]arene (<b>EtP5</b><i>α</i>) showed no adsorption of <i>cis</i>-<b>G</b> and <i>trans</i>-<b>G</b>, while NACs of perethylated pillar[6]arene (<b>EtP6</b><i>β</i>) exhibited high selectivity for <i>cis</i>-<b>G</b> either by solid-vapor adsorption or solid-liquid adsorption with the purity of 96.25 and 97.73%, respectively. Meanwhile, <b>EtP6</b><i>β</i> can be recycled five times without loss of selectivity, indicating excellent cycling performance of <b>EtP6</b><i>β</i>.