Effective Adsorption of Cyclohexene and Analytically Perfect Separation of Cyclohexene/Cyclohexanol Azeotropes by Nonporous Adaptive Crystals of a Hybrid[3]arene

Cyclohexene is an important volatile organic compound
(VOC), which
is the key raw material for the preparation of cyclohexanol. Because
of the formation of azeotropes between cyclohexene and cyclohexanol,
the separation of cyclohexene and cyclohexanol is extremely challenging.
However, there are some challenges for conventional separation methods,
such as complex equipment, high operating costs, and huge energy consumption.
Herein, we present an energy-efficient adsorptive separation method
to effectively adsorb cyclohexene and selectively separate cyclohexene
from cyclohexene and cyclohexanol azeotropes with a purity of 100%
using nonporous adaptive crystals of a hybrid[3]arene H (Hα). As revealed by the single crystal structure,
multiple noncovalent interactions between H and cyclohexene
are responsible for the perfect selectivity. Density functional theory
calculations explain in detail the mechanism of the preferential adsorption
of cyclohexene and the selective separation of cyclohexene and cyclohexanol
azeotropes by Hα. Moreover, the recovery and recycling
of Hα by dissolving Hα that
adsorbed cyclohexene in ethanol are reported for the first time. It
is anticipated that this work will provide valuable and timely insights
for the separation of azeotropes by nonporous adaptive crystals and
the interpretation of selective separation using theoretical calculations.