Nat. Commun.: new progress in the study of rare earth separation based on the synergistic effect of supramolecular components

Rare earth is an indispensable raw material for modern industry and an important strategic resource in China Due to its special electronic configuration, rare earth elements are widely used in batteries, electronic equipment, contrast agents, permanent magnet materials, superconducting materials and catalyst preparation Rare earth elements are abundant in the earth's crust, but most of them are associated minerals With the continuous consumption of rare earth resources, concentrate grade, smelting extraction and recycling become the key scientific issues to be solved in the development of rare earth industry Sun Qingfu research group and its collaborators, State Key Laboratory of structural chemistry, Fujian Institute of physical composition, have recently realized one-step high-efficiency separation of rare earth, rare earth transition metal and rare earth alkaline earth metal based on supramolecular synergy In the previous work, the team found that there was a strong ligand synergy in the tetrahedral structure of LN 4L 4 formed by self-assembly of 2,6-pyridyldiamide tripod tridentate ligand (L) and lanthanide metal (LN) Recently, the team found that these ligands have a high degree of assembly adaptability, and can be self-assembled with alkaline earth, transition and rare earth metals at the same time to obtain heteroisomeric m4l4 (M = CA II, CD II and LN III) type supramolecular tetrahedrons It is found that the CA II or CD II ions in the tetrahedral structure also have the nine coordination structure of the triangular prism, which is very rare in coordination supramolecular chemistry At the same time, due to the synergistic effect of supramolecular components, the tetrahedral structure has high stability in the presence of excessive ligands or metal ions As a contrast, single and double arm ligands with the same coordination site as L form mononuclear and binuclear assemblies respectively, but the structural stability of the assemblies is weak, that is, in the presence of excessive metal ions or ligands, the original structures will be destroyed and new dynamic complexes will be formed In addition, m4l4 tetrahedron has a high degree of metal self-classification and collaborative self-assembly behavior In the self-assembly process of multi-component mixed metal ions, ligand L has a super high selective recognition ability for different metal ions The experimental results show that the ligand l can realize one-step ion self-assembly of alkaline earth metal CA II, transition metal CD II and rare earth metal ln III: in the mixed system of CA II / ln III (1:1) and CD II / ln III (1:1), the ligand l selectively only coordinates with rare earth metal At the same time, for the mixed rare earth ion pairs with more similar chemical properties, when the radii of the two rare earth ions differ greatly, ligand l can completely separate the two metals, such as La III / EU III with a difference of 0.10 μ M Metal pair; even for the mixed rare earth ion pair with small difference in ion radius, ligand l can also achieve efficient separation of two rare earth ions, for example, for La III / CE III metal pair with a difference in ion radius of only 0.02 μ, the resulting assembly contains 89.3% Ce III and 10.7% La III According to this, the difference of coordination stability constants between the two kinds of rare earth tetrahedrons is more than 3.6 orders of magnitude Finally, based on tripod tridentate ligands, highly selective self-assembly of metal ions was carried out By introducing long fatty chains into the end of ligands for functionalization, the solubility or dispersion of the assembly in low polar organic solvents can be increased, and the practical operation of this kind of metal separation and extraction system can be conceptually demonstrated In view of the similarity of the chemical properties of lanthanum and actinides, it can be predicted that this new super molecular synergistic extraction strategy will have a bright future in the recycling of radioactive nuclear waste Paper link: https://www.nature.com/articles/s41467-018-02940-7 corresponding author: Sun Qingfu http://www.fjirsm.ac.cn/yjsjy/dsjj/sssds/sqf/jean claudeb ü nzli http://iam.njtech.edu.cn/en/view.asp? Id = 459 & class = 7