Russian Research Team Synthesizes Novel Metal-Organic Framework Material Capable of Immobilizing Radioactive Cesium

The Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences has synthesized a novel metal-organic framework material containing neptunium and cesium atoms. Research shows that this material is insoluble in water, resistant to high temperatures and intense radiation, and can stably “lock” radioactive cesium within its own structure, offering new insights for research on radionuclide immobilization and radioactive waste treatment materials.

Metal-organic framework materials are a class of materials with high porosity and controllable crystal structures, whose lattices are typically composed of metal atoms connected by organic molecules. Since their pore sizes and structures can be tuned at the molecular level, these materials can be used to adsorb gases or specific nuclides. However, compared with traditional adsorbents such as activated carbon, metal-organic framework materials have higher synthesis costs and are currently at a stage of more frontier research and exploration of specific applications.

According to the researchers, this new material was obtained during radiochemical synthesis experiments on f-element metal-organic frameworks. The team originally intended to promote the formation of specific stable frameworks by irradiating starting materials with accelerated electron beams or ultraviolet light. While investigating neptunium-related reactions, the researchers discovered a new substance whose structural units differed from those of known materials, and conducted a structural analysis of it.

The analysis results showed that the material is a bimetallic framework containing neptunium and cesium, with a lattice composed of four neptunium atoms and two cesium atoms connected via oxygen bridges, and a pore size of approximately 2.69 Å. Experiments demonstrated that the material is insoluble in water, does not degrade when heated to 400 degrees Celsius, and can withstand radiation doses of up to 6 megagrays.

The research also found that cesium is tightly integrated into the framework structure and does not participate in ion exchange. Using cesium-137 as a tracer, the researchers observed no leaching or release of cesium-137 from the material into solution. This indicates that the material has potential application value in the immobilization of radioactive cesium and may serve as one of the candidate matrices for the vitrification or ceramization stage of radioactive waste treatment in the future.

The researchers also noted that, due to the high cost of metal-organic frameworks based on neptunium and cesium, their economic viability as conventional adsorbents still requires evaluation. In contrast, metal-organic framework materials may hold greater application prospects in areas such as supports for catalytic reactions, for example, by introducing catalytically active elements into the pores to prepare heterogeneous catalysts.

The institute is also exploring the synthesis of metal-organic framework materials using electron accelerators and ultraviolet radiation. Compared with traditional prolonged heating methods in autoclaves, electron accelerator synthesis can be completed within minutes and is expected to improve yields while reducing energy consumption and costs. The researchers stated that such methods may help obtain more novel framework structures based on different metals.