Syntheses,Structures And Properties Of Metal Organic Frameworks Based On Triazole-Carboxylic Acid Ligands

Metal organic frameworks?MOFs?are a class of crystalline porous materials with periodic network structure formed by inorganic metal centers?metal ions or metal clusters?and bridged organic ligands interconnected by self-assembly.In this papar,two kinds of triazole-carboxylic acid ligands were selected,and 12 new metal-organic frameworks were obtained by solvothermal method with rare earth metal salts and transition metal salts,respectively.The structures were measured by single crystal X-ray diffraction,and their properties were studied by IR,UV-vis,PXRD and so on.In conclusion,nine rare earth-MOFs belong to the isomorphic MOFs,and among them,Eu-MOF was firstly selected to explore the related properties of this series of MOFs.It can be found that Eu-MOF can not only efficiently,repeatly and rapidly absorb Congo red dye,but also selectively identify Fe³⁺,Cr₂O₇^2-,Al³⁺,Cr²⁺and organic solvents such as acetone,nitrobenzene and aniline.As to the other three MOFs of transition metals,it was found that complex10 can recognize DMSO and Cr₂O₇^2-by fluorescence.complex11 has a weak adsorption effection on the dyes within 30 min.The electrochemical properties of complex 12 and its modified composite materials were studied,but almost no hydrogen and oxygen evolution properties were found.The main contents are listed below:1?3,5-di-?triazol-1-yl?-benzoic acid?L1?and Ln?NO₃?₃?xH₂O?Ln=Eu,Tb,Gd,Y,Dy,La,Ho,Nd,Yb?were used to obtain 9 rare earth MOFs.X-ray single crystal diffraction shows 9 rare earth-MOFs are isomorphic MOFs.Then Eu-MOF was firstly selected to study the related properties of nine MOFs.It was found that the the metal center Eu³⁺can coordinate with the nitrogen and oxygen atoms of the ligand,and these oxygen and nitrogen atoms were further linked with Eu ions to obtain a mesoporous three-dimensional metal organic framework.UV-Vis spectroscopy shows that Eu-MOF can adsorb Congo red dye on the surface,and it also can quickly adsorb Congo red dye after 3 recycles.Additionally,under the excitation of 298 nm,the fluorescence luminescence spectrum shows that the complex can be significantly enhanced by fluorescence emission intensity to detect Al³⁺and Cr²⁺with high sensitivity and low detection limit,and can detect Fe³⁺,Cr₂O₇^2-,nitrobenzene and aniline derivatives by fluorescence quenching.This shows that the prepared Eu-MOF can not only adsorb the Congo red dye with high efficiency and repeatability,but also can be used as a fluorescent sensor to identify Fe³⁺,Cr₂O₇^2-,Al³⁺,Cr²⁺and acetone,nitrobenzene,aniline and other small organic molecules.Based on this experiment,the mechanism was also discussed.2?L1 and 2,4-di-?triazol-1-yl?-benzoic acid?L2?are reacted with Zn?NO₃?₂?6H₂O and CuSO₄ respectively to obtain three transition metal MOFs at appropriate temperatures.The nitrogen and oxygen atoms of the ligands can all coordinate with the metal center.L1 and Zn?NO₃?₂?6H₂O were used to obtain a two-dimensional metal-organic framework,the interaction between L2 and Zn?NO₃?₂?6H₂O is one-dimensional chain and CuSO₄ is three-dimensional MOFs.The researches were carried on based on our former work.Thus,the fluorescence emission study of complex 10 shows that it can detect Cr₂O₇^2-and DMSO molecules.complex11 has a weak adsorption effect on the dyes within 30 minutes.The electrochemical properties of complex 12 and its modified composite materials were studied,but almost no hydrogen and oxygen evolution properties were found.