Design And Synthesis Of Uranium And Thorium Metal-organic Frameworks And Properties Of Gas Adsorption And Photocatalytic

As a representative of new porous materials,Metal-organic frame materials(MOFs),have many unique advantages compared with traditional porous materials,such as high porosity,large specific surface area,frame structure,pore size,adjustable channel functional groups and easy functionalization.The structural characteristics of MOFs not only enable them to be used as adsorbents to store clean fuel gases,but also can produce different hoster-guest interactions for different gas molecules to achieve selective separation of mixed gases.In addition,MOFs are also suitable as catalysts because of their frame structure,which enables the efficient transfer of electrons and active intermediates between different components.Compared with MOFs materials of transition metals and lanthanide metals,the uniqueness of MOFs materials based on actinide metal is not only that people have less explored them,but also the uniqueness of actinide ions in bonding and coordination.The uranyl 2D metal-organic framework nanosheets(MONs),due to the ordered pores perpendicular to the sidewalls,high active site exposure ratio,and abundant reachable active sites in the channel,provide an alternative to the development of traditional catalysts.In paper,we synthesized new MOFs based on thorium/uranium metal ions and tricarboxylic acid ligands H₃L,NH₂-BTB,BTB.And thier adsorption/separation for gas and photocatalytic properties were studied.In the first chapter,MOFs and their applications in gas adsorption-separation and catalysis are briefly introduced.In the second chapter,a new thorium metal-organic framework material[NH₂(CH₃)][Th₂(H₂O)₂(L)₃](namely ECUT-36),which was synthesized by Th(NO₃)₄�4H₂O and H₃Lthrough the solvent thermal(H₃L=4,4',4''-triformic acid trianiline).Its basic building block is Th₂dual-core structure,showing a new(3,9)-connected topological structure,using(4²6)(4⁶6²¹8⁹)Schlafli symbolic representation.The study showed that[NH₂(CH₃)]⁺protons in the pores were transferred to the ligand carboxyl oxygen atom after heat treatment,which made the material exhibit high porosity and showed potential in hydrogen deuterium separation and ammonia capture application.In the third chapter,two crystals ECUT-100[(UO₂)(NH₂-BTB)][NH₂(CH₃)₂]and ECUT-101[(UO₂)(BTB)][NH₂(CH₃)₂]were synthesized based on UO₂(NO₃)₂�6H₂O and1,3,5-(tri-benzoic acid)aniline(NH₂-BTB),4,4',4''-benzene-1,3,5-triyl-tri-benzoic acid(BTB),respectively.By adjusting the functionalized unit(NH₂-group)in the organic ligand,the overlapping stacking model of ECUT-101 was transformed into the staggered stacking model of ECUT-100.Two novel uranyl metal-organic frame nanosheets were successfully synthesized by simple"top-down"exfoliation.The thickness of ECUT-100-N is about 1nm,and that of ECUT-101-N is about 3nm.DFT calculations show that the reactant molecules are more readily accessible to the uranyl ions of ECUT-100-N.Therefore,the conversion number(TON)of ECUT-100-N photocatalytic oxidation of benthylene sulfide is about 2.2 times that of ECUT-101-N.In addition,the TON values of ECUT-100-N and ECUT-101-N are 4.5 times and 2.3 times higher than those of the original uranyl MOFs,respectively,due to the more easily accessible active sites,faster charge transfer and higher separation efficiency of photogenic electron-hole pairs in uranyl MONS.