Single-crystal-to-single-crystal (SCSC) transformation of anion-adaptive material, SCP-IHEP-1, upon ReO₄^- incorporation.

 With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences, the research group led by Prof. Wei-qun Shi , at Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, designed and synthesized a new kind of supramolecular sorbent as bulk-material anion ‘receptor’ for effective removal of radioactive 99TcO4−, which was published in Nature Communications (2019, 10 (1), 1532).

   Vigorously developing nuclear power is an important option  for energy structure upgrading in China. Nuclear waste treatment related with nuclear fuel cycle is facing unprecedented challenges. At the current stage, there are tremendous basic research needs in this field to guarantee its sustainable development. For instance, versatile tailored materials for radio nuclide elimination via solid-phase extraction based separation are enormously desirable with respect to prevention and control of environmental radioactive pollution.

   On the other hand, supramolecular ligands materials incorporating weak interactions between host molecules and target ions have shown broad application prospects. Before this breakthrough on supramolecular anion receptor of 99TcO4−, Shi’s group have studied the coordination interactions and assembly behaviors of supramolecular pseudorotaxane with actinide cations, and successfully synthesized the first actinide-organic polyrotaxane compound(Chemical Communications2014, 50, 3612) and the first neptunyl-organic rotaxane compounds (Chemical Communications2018, 54, 8645), which are expected to be potentially novel solid waste forms for radionuclide solidification.

    Actually, efficient anion recognition still remains a problem with regard to radioactive 99TcO4- decontamination. It is encouraging that they prepared a class of supramolecular soft materials based on cucurbit uril through a multi-component assembly strategy and used it as an adsorbent to effectively capture 99TcO4-. The selectivity of this as-synthesized material is one of the most competitive among the metal organic materials (MOM) reported so far. Single crystal structure analysis clearly identifies the periodical presence of ReO4- (a non-radioactive surrogate of 99TcO4-) in the adsorbent after anion exchange experiment, which forcefully reveals the mechanism for its selectivity toward TcO4-/ReO4-, that is, the supramolecular framework performs adaptive reconstruction of the supramolecular skeleton after anion exchange, thereby promoting effective identification and separation of TcO4-/ReO4-. The tactic put forward in the Nature Communications paper would provide a new design concept for the subsequent development of decontamination materials toward radionuclides based on anion recognition with improved separation selectivity.