The effective and safe capture and
storage of radioactive iodine (129I or 131I)
is of significant importance during nuclear waste storage and nuclear
energy generation. Here we present detailed evidence of highly efficient
and reversible iodine capture in hexaphenylbenzene-based conjugated
microporous polymers (HCMPs), synthesized via Buchwald–Hartwig
(BH) cross-coupling of a hexakis(4-bromophenyl)benzene (HBB)
core and aryl diamine linkers. The HCMPs present moderate surface
areas up to 430 m2 g–1, with narrow pore
size distribution and uniform ultramicropore sizes of less than 1
nm. Porous properties are controlled by the strut lengths and rigidities
of linkers, while porosity and uptake properties can be tuned by changing
the oxidation state of the HCMPs. The presence of a high number of
amine functional groups combined with microporosity provides the HCMPs
with extremely high iodine affinity with uptake capacities up to 336
wt %, which is to the best of our knowledge the highest reported to
date. Two ways to release the adsorbed iodine were explored: either
slow release into ethanol or quick release upon heating (with a high
degree of control). Spectral studies indicate that the combination
of microporosity, amine functionality, and abundant π-electrons
ensured well-defined host–guest interactions and controlled
uptake of iodine. In addition, the HCMPs could be recycled while maintaining
90% iodine uptake capacity (up to 295%). We envisage wider application
of these materials in the facile uptake and removal of unwanted oxidants
from the environment.
A crepuscular catalyst: Alkene migration catalyzed by [(RCN)2PdCl2] complexes proceeds through an in situ generated Pd‐H species. Addition of a 1,5‐diene inhibits migration and allows the slower background catalysis of E/Z interconversion to be studied. Experimental and computational results suggest this interconversion proceeds through a conformational equilibrium in dipalladacycles (see picture).
The influence of processing conditions on the thin film microstructure is a fundamental question that must be understood to improve the performance of solution-processed organic electronic materials. Using grazing-incidence X-ray diffraction, we have studied the structure of thin films of a tetra(aniline)-surfactant complex prepared by drop-casting from five solvents (hexane, chloroform, tetrahydrofuran, dichloromethane and ethanol), selected to cover a range of polarities. We found that the structure, level of order and degree of orientation relative to the substrate were extremely sensitive to the solvent used. We have attempted to correlate such solvent sensitivity with a variety of solvent physical parameters. Of particular significance is the observation of a sharp structural transition in the thin films cast from more polar solvents; such films presented significantly greater crystallinity as measured by the coherence length and paracrystalline disorder parameter. We attribute this higher structural order to enhanced dissociation of the acid surfactant in the more polar solvents, which in turn promotes complex formation. Furthermore, the more polar solvents provide more effective screening of (i) the attractive ionic interaction between oppositely charged molecules, providing greater opportunity for dynamic reorganisation of the supramolecular aggregates into more perfect structures; and (ii) the repulsive interaction between the positively charged blocks permitting a solvophobic-driven aggregation of the aromatic surfaces during solvent evaporation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.