Synthesis,structures And Properties Of Three Dimensional Porous Uranyl Organic Framworks

As we all know,coordination chemistry,as an important branch of chemistry,promotes the rapid development of chemistry.Coordination polymers have been widely used in gas storage and separation,ion exchange,sensing,catalysis and other fields.At present,the coordination behavior and related functions of transition metals and lanthanide metals have been comprehensively recognized,but the research on the synthesis,structure and properties of actinide complexes is still in the preliminary stage.Uranium is the grain of nuclear fuel in nuclear power plant and has rich 5f electronic structure.Studying the coordination behavior of uranium and building functional materials based on uranium can not only understand the coordination properties and electronic structure of uranium,but also provide experimental and theoretical basis for the extraction and decontamination of uranium in nuclear fuel cycle,expand and develop functional materials based on uranium.At present,there are only a few studies on the fluorescence and photocatalytic degradation of uranyl complexes,and most of the reported uranyl complexes are one-dimensional or two-dimensional structures,with stable three-dimensional porous structure is rare.Therefore,it is of great significance to construct a stable three-dimensional porous uranyl organic framework and explore its functions.In view of this,this paper reports two rare three-dimensional porous uranyl organic frameworks and their gases separation research.(1)Firstly,9,10-bis(4-carboxyphenyl)anthracene(H₂L)was selected as the organic ligand and adopted high temperature solvothermal synthesis.700?L concentrated nitric acid was added into the reaction system,H₂L and uranyl cation UO₂²⁺were self assembled to form a periodic three-dimensional uranyl organic framework[(UO₂)₂(O₂)L₂][NH₂(CH₃)₂]₂(UOF-1)at 185?.There is only one coordination mode of metal U in UOF-1,the coordination number is 7,which constitutes a pentagonal biconical geometry.It is worth noting that uranyl ions are connected by peroxy ions,which can be further confirmed by Raman spectroscopy and potassium iodide solution of starch.As far as we know,this is the first case of uranyl organic framework bridged by peroxy ions in the world.More importantly,the peroxy ion bridge of activated samples still exists stably.The study of gas adsorption shows that UOF-1has potential application value in the separation of CO₂,C₂H₄,C₂H₂and C₂H₆.(2)Then this study designed a triangular twisted ligand:1,3,5-trimethyl-2,4,6-tris(4-carboxyphenyl)benzene(H₃CTTA).Using mixed solvothermal method,at 150?,H₃CTTA and uranyl cation UO₂²⁺self-assembled to construct a rare stable three-dimensional porous inserted uranyl organic grid[UO₂(CTTA)]H,referred to as UOF-2.There is only one coordination mode of uranium in UOF-2 and the coordination number is 8,which forms a hexagonal biconical geometry.The stability of UOF-2 was studied by means of powder X-ray diffraction and thermogravimetry.The results showed that the stability of UOF-2 was excellent,and the structure remained stable after gas adsorption.Gas adsorption study shows that the specific surface area of the activated UOF-2 is 1638 m²/g,which surpasses most actinide complexes at present.Besides,UOF-2 can potentially separate a variety of mixed gases that cannot be separated by traditional materials at present,such as CO₂/C₂H₂,C₂H₄/C₂H₆,C₂H₄/C₃H₆and Xe/Kr.It can be said that UOF-2 is a multi-purpose separation material.