Design,Synthesis And Application Of Actinide-based Metal-Organic Frameworks With Polydentate Carboxylate Ligands

With the rapid development of nuclear power industry in China,it is urgent to find a suitable method for spent fuel reprocessing(SFR),within which actinides represent the main target to deal but this remains unsolved issue due to the complex forms of actinide species and the extremely harsh conditions in SFR.Metal-organic frameworks(MOFs)are a class of porous crystalline coordination polymers constructed from metal nodes and organic linkers.Since the first report,MOFs have broad application prospects in fields such as catalysis,adsorption and separation,drug carriers,and energy storage due to their diverse synthesis methods,strong stability and tunable structures.Actinide-based MOFs have shown abundant coordination geometries and topologies than other metal-based MOFs because of the variable valence state and high positive charge of the actinide center.Therefore,the study of the structure and properties of actinide MOFs is promising to provide a theoretical basis for the separation and solidification of radionuclides and a reference value for the spent fuel reprocessing.In this thesis,several novel U/Th-MOFs were synthesized under solvothermal conditions using flexible tridentate carboxylic acids and pyridine-based carboxylic acids as organic ligands and uranium/thorium as metal nodes:(1)Under solvothermal conditions,complexes U-SYD and Th-SYD were synthesized by self-assembly of organic ligand 1,3,5-tri(4-carboxyphenoxy)benzene with uranyl nitrate and thorium nitrate,respectively.The structures of the complexes were characterized by X-ray single crystal diffraction.The results showed that the USYD displays a two-dimensional layered structure and the Th-SYD displays a threedimensional microporous structure.Then the two complexes were characterized by Xray powder diffraction,BET,TG,UV-Vis absorption spectra.In addition,the X-ray detection performance of U-SYD and Th-SYD was evaluated and the result showed that they both could transform the X-ray into electrical signal,the sensitivity of X-ray detection is 0.3μCGy-1cm-2 and 0.24μCGy-1cm-2,respectively.The excellent X-ray blocking ability endows the U-SYD with similar detection performance with the commercial detector materials α-Se,and the Th-SYD with even better performance thanα-Se.(2)Under solvothermal conditions,2,2’-bipyridine-5,5’-dicarboxylic acid and thorium nitrate were used as reactants to synthesize Th-BPYDC-I complexes.The structures of complex Th-BPYDC-I were characterized by X-ray single crystal diffraction.And the results showed that the Th-BPYDC-I displays a three-dimensional microporous structure.At the same time,complex Th-BPYDC-I were characterized by X-ray powder diffraction,BET,TG.In addition,in order to study the effect of materials on the adsorption and separation of Xe/Kr,the adsorption and separation tests of complexes Th-BPYDC-I were carried out.The results showed that the adsorption capacity of complex Th-BPYDC-I for Xe was 2.059 mmol/g and that for Kr was 0.614 mmol/g at 298 K.The Henry coefficient of the complex Th-BPYDC-I was studied and compared,and it was found that the separation ratio of the material to Xe/Kr was 7.49.