Design And Synthesis Of Actinide Metal-organic Frameworks Based On Carboxylic Acid Ligands And Their Applications In Catalysis And Adsorption

The development of radioactive pollution control has significant implications for the environment and public health.Actinide elements are the most abundant elements in spent fuel,with transuranic elements exhibiting strong radioactivity and radiotoxicity.The properties of low-level radioactive uranium,thorium,and their derivatives can be studied to simulate the chemical behavior of transuranic elements considering the similar physical and chemical properties of actinide elements Unlike the extensively studied coordination polymers of transition metals and lanthanide metals,research on the synthesis,structure,and properties of actinide metal coordination compounds is still in its infancy.By studying the coordination characteristics and potential applications of uranium and thorium coordination polymers,not only can their coordination properties and electronic structures be understood,providing experimental and theoretical basis for the separation and solidification of actinide elements in nuclear fuel cycles,but also functional materials based on uranium and thorium elements can be developed and expanded,achieving the transformation from waste to functional materials.The treatment of spent fuel is also closely related to the development of nuclear medicine.The radioactive isotopes used in nuclear medicine diagnosis and treatment mainly come from reactors,and the improvement of spent fuel treatment technology can provide significant help for the production of radiopharmaceuticals.The study of actinide elements is of crucial importance to both the sustainable development of nuclear energy and the development of nuclear medicine.In this study,porous actinide based metal organic framework materials was synthesized using hydrothermal and solvothermal methods,by selecting appropriate ligands and adjusting reaction conditions.This includes a rare bimetallic organic framework material(SCU-16-U)with dual actinide nodes and catalytic function,as well as a microporous thorium-based organic framework material(SCU-17)with good stability and iodine adsorption performance.The specific research contents are as follows:(1)3,5-dicarboxyphenylpyridine(H2L)was selected as the organic ligand to selfassemble with tetravalent thorium ions via a solvothermal method,forming a threedimensional thorium-based metal-organic framework[Th6O4(OH)4(UO2)0.5(HCOO)5(CO3)1.5(L)3(H2O)3]·10H2O·3DMF·NH2(CH3)2,abbreviated as SCU-16.To our knowledge,this is currently the largest known singlecell volume thorium-based MOF.There exists a coordination site formed by formate anions in SCU-16.Due to a conformational mismatch,this site cannot directly coordinate uranyl ions with a planar coordination configuration.However,under oxidizing conditions,this site can be transformed in situ into a pre-organized coordination site rich in carbonate anions via a "formate-to-carbonate" reaction.The new site perfectly matches the coordination configuration of uranyl ions,resulting in a long-range ordered uranyl-thorium heterobimetallic crystalline structure(SCU-16-U).Single-crystal X-ray diffraction,X-ray photoelectron spectroscopy,scanning electron microscopy,and other results fully confirm the formation of the heterobimetallic MOF and its structural order.This unique reaction-induced pre-organization strategy can construct complex heterobimetallic crystalline structures.Furthermore,the introduction of additional actinide ions endows the material with diverse catalytic properties.SCU16-U exhibits catalytic properties derived from both thorium and uranium,making it a potential bifunctional catalyst.The reaction-induced pre-organization strategy proposed in this work provides a new pathway for the preparation of mixed actinide element functional materials with unique structures and multifunctionality.(2)131I and 125I are the most commonly used medical radioisotopes in nuclear medicine for diagnosis and treatment,primarily produced from reactors.Iodine leakage can pose a great threat to people’s health.The proper disposal of iodine can reduce the risk of radioactive iodine leakage,which is of great help to the corresponding development of nuclear medicine In this work,a microporous thorium-based organic framework material(SCU-17)was constructed using(1,1,3,1-tetraphenyl)-4,4dicarboxylic acid-5-methyl(H2L-CH3)as the organic ligand and thorium ions as the metal nodes.Due to the material’s excellent stability,appropriate microporous channels,and hydrophobic groups in the ligand,the material exhibited excellent iodine vapor adsorption performance(1.1 g/g).This work provides support for the design of adsorbents for radioactive iodine isotopes.