Separation of Cyclohexanone and Cyclohexanol by Adaptive Pillar[5]arene Cocrystals Accompanied by Vapochromic Behavior

The separation of cyclohexanone (CHA-one) and cyclohexanol(CHA-ol)mixtures is of great importance in the chemical industry. Currenttechnology exploits multiple steps of energy-intensive rectificationdue to their close boiling points. Herein, we report a new and energy-efficientadsorptive separation method employing binary adaptive macrocyclecocrystals (MCCs) built with & pi;-electron-rich pillar[5]arene(P5) and an electron-deficient naphthalenediimide derivative (NDI)that can selectively separate CHA-one from an equimolar CHA-one/CHA-olmixture with >99% purity. Intriguingly, this adsorptive separationprocess is accompanied by vapochromic behavior from pink to dark brown.Single-crystal and powder X-ray diffraction analyses reveal that theadsorptive selectivity and vapochromic property are derived from theCHA-one vapor inside the cocrystal lattice voids triggering solid-statestructural transformations to yield charge-transfer (CT) cocrystals.Moreover, the reversible transformations make the cocrystalline materialshighly recyclable.

Automated summary

This article reports a new and energy-efficient adsorptive separation method using reversible solid-state structural transformations in MCCs. The selectivity of CHA-one and CHA-ol is achieved by triggering solid-state structural transformations through CHA-one vapor.