Near-perfect separation of alicyclic ketones and alicyclic alcohols by nonporous adaptive crystals of perethylated pillar[5]arene and pillar[6]arene

The separation of alicyclic ketones and alicyclic alcohols is one of the challenges in the field of petrochemical industry. However, traditional separation methods suffer from excessive energy consumption, complicated operation, and unsatisfactory separation efficiency for substances with similar boiling points. Herein, we offer an innovative method for the separation of alicyclic ketones and alicyclic alcohols employing nonporous adaptive crystals (NACs) of perethylated pillar[5]arene (EtP5) and perethylated pillar[6]arene (EtP6). NACs of EtP5 cannot adsorb either alicyclic ketones or alicyclic alcohols because of the small cavity size of EtP5. By contrast, NACs of EtP6 can separate cyclopentanone from the vapor mixture of cyclopentanone/cyclopentanol (v:v = 1:1) and cyclohexanone from the vapor mixture of cyclohexanone/cyclohexanol (v:v = 1:1) with purities of 99.1 % and 100 %, respectively. Density functional theory calculations show that the selectivity comes from the thermodynamic stability of the newly formed crystal structure after adsorption of the preferred guest molecule. Moreover, NACs of EtP6 can be reused without losing selectivity and performance.