Reversible Iodine Capture by Nonporous Pillar[6]arene Crystals

Here we report that easily obtained per-ethylated
pillar­[6]­arene (EtP6) is a new adsorbent for iodine capture
with high chemical and thermal stability. Nonporous EtP6 solids are shown to capture not only volatile iodine in the air
but also iodine dissolved in an organic solvent and aqueous solution.
Uptake of iodine leads to a structural transformation of EtP6 in the solid state. In the single crystal structure of iodine-doped EtP6 (I2@EtP6), each adsorbed iodine
molecule is located between two adjacent EtP6 molecules
to form a linear supramolecular polymer. Iodine is released spontaneously
from I2@EtP6 solids when they are immersed
in cyclohexane. These EtP6 solids can be reused many
times without losing iodine capture capacity.