Functional Uranyl-organic Complexes:Synthesis,Structure And Properties

Metal organic framework(MOFs)materials are a kind of organic-inorganic hybrid materials formed by coordination bonds between organic ligands and metal ions.In recent years,with the further investigation of MOFs materials,it has been found that MOFs have potential applications in the fields of gas adsorption separation,ferroelectrics,sensors,fluorescence and catalysis.In this paper,uranium has been selected as the central metal ion of MOFs material,and a series of oxygen-containing carboxylic acid ligands are introduced to synthesize navel MOFs material.Six MOFs materials are synthesized by hydrothermal method and the obtained products are characterized by a kind of methods such as X-ray Diffraction(XRD),Single Crystal X-ray Diffraction(SCXRD),Fourier Transform Infrared Spectroscopy(FT-IR),Ultraviolet-visible(UV-vis)Spectroscopy and Thermo-gravimetric analysis(TGA).The photocatalytic properties of the MOFs materials were also studied.The details are as follows:(1)The Uranyl complexes of thiophenemalonic acid:thiophenic acid was used as the ligand,deionized water was used as solvent,uranyl nitrate was used as central metal,the p H was adjusted by Na OH solution,and then the Complex 1([(L1)₂(OH)₈(UO₂)₆]·7H₂O)was obtained;On the basis of Complex 1,the organic solvent NMP and cupric nitrate was added to the solution and the obtain the Complex2([(L1)₂(bipy)₂(C₂O₄)Cu(OH)₂·H₂O]·3H₂O).In the Complex 1,there are three independent crystallographic uranium centers,all of which are seven-coordinated;at the same time the Complex 2 contains a uranium center and formed by 8 coordination mode.Both of Complex 1 and 2 are two-dimensional layered structures.Meanwhile,the FT-IR,UV-vis spectrum,Fluorescence spectrum,TGA and photocatalytic activity of Complex 1 were also has been investigated.(2)Two uranyl complexes([(L2)(UO₂)](Complex 3),[(L2)(UO₂)NMP](Complex 4))were synthesized,using 2,4'-diphenyldicarboxylic acid as a ligand.Both complexes 4 and 3 contain only a uranium center and formed by 7-coordination mode,and then the ligands participated in coordination by deprotonation,so that the Complexes 4 and 3 form a two-dimensional layered structure.The fluorescence and photo-catalytic activities of Complexes 4 and 3 has been investigated,systematically.(3)Other Two uranyl complexes([(L3)₂(UO₂)₅(?-OH)₄]·7H₂O(Complex 5)),[(L3)₂(UO₂)₃(H₂O)₃]·2H₂O(Complex 6))were synthesized using ligand5-nitro-1,2,3-benzenetricarboxylic acid as ligand,.In the Complex 5,the uranium center was formed via seven-coordinate and eight-coordinated,while the uranium center in the Complex 6 was a seven-tooth coordination mode.They are connected by ligand L3(a completely deprotonated)and formed a two-dimensional layered structure.The investigation of fluorescence and photo-catalytic activity shows that the Complexes 5 and 6 have a high efficiency for photo-catalytic degradation for Rhodamine B on solution under the condition of simulated sunlight.