Nuclear energy plays an important role in energy supply. The recovery of nuclear waste such as radioactive iodine pollutants has attracted great attentions. To identify the adsorption binding of radioactive elements and understand the adsorption mechanism are of great significance.
In a study published in J. Am. Chem. Soc., the research group led by Prof. ZHANG Jian and Prof. FANG Weihui from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a series of mesoporous materials assembled by aluminum molecular rings as iodine adsorbents.
The researchers first employed pyrazole-thermal synthesis in the preparation of aluminum oxide-clusters (AlOCs), and obtained a series of Al8 aluminum molecular rings (AlOC-15- AlOC-25) by using pyrazole derivatives and carboxylic acid ligands. The bandgap and surface wettability can be controlled by adjusting the types of peripheral organic ligands.
Through the introduction of structural modifiers, the stacking mode of AlOC-26-NC was transformed from nanotubes to cubic supramolecular nanocages (AlOC-26-NC to AlOC-29-NC). These supramolecular nanocages have both mesoporous (21.19 Å) and microporous channels (7.8 Å). The results of iodine vapor adsorption experiments showed that the supramolecular nanocages have good iodine adsorption performance (50.3 wt%).
The researchers then identified the adsorption sites of iodine molecules by single-crystal X-ray diffraction, which are ordered in the micropores of the supramolecular cage under the I…π (4.72 Å and 3.81 Å) interaction.
This kind of supramolecular cage can be recycled. AlOC-22 (nanotube) and AlOC-26-NC (nanocage) are a pair of isomers with the same molecular formula but obviously different iodine adsorption performances, which are closely related to their structural types.
This study realized the mesoporous supramolecular assembly of aluminum molecular rings and crystallographic visualization of iodine adsorption binding and mechanisms. It indicated the promising application of supramolecular materials as adsorbents in the capture and storage of fission product gases.
Featured image: Assembly of aluminum molecular rings and iodine adsorption (Image by Prof. ZHANG’s group)
Reference: Shuyang Yao, Wei-Hui Fang, Yayong Sun, San-Tai Wang, and Jian Zhang, “Mesoporous Assembly of Aluminum Molecular Rings for Iodine Capture”, J. Am. Chem. Soc. 2021.
Provided by Chinese Academy of Sciences