Actinide Separation Inspired by Self-Assembled Metal–Polyphenolic Nanocages

The
separation of actinides has a vital place in nuclear fuel reprocessing,
recovery of radionuclides, and remediation of environmental contamination.
Here we propose a new paradigm of nanocluster-based actinide separation,
namely, nanoextraction, that can achieve efficient sequestration of
uranium in an unprecedented form of giant coordination nanocages using
a cone-shaped macrocyclic pyrogallol[4]­arene as the extractant. The
U24-based hexameric pyrogallol[4]­arene nanocages with distinctive
[U2(PG)2] binuclear units (PG = pyrogallol)
that rapidly assembled in situ in monophasic solvent were identified
by single-crystal X-ray diffraction, MALDI-TOF mass spectrometry,
NMR spectroscopy, and small-angle X-ray and neutron scattering. Comprehensive
biphasic extraction studies showed that this novel separation strategy
has enticing advantages such as fast kinetics, high efficiency, and
good selectivity over lanthanides, thereby demonstrating its potential
for efficient separation of actinide ions.