Preparation And Sensing Properties Of Lanthanide Metal-Organic Frameworks Material(Ln-MOFs) Based On Polycarboxylic Acid Ligands

Metal organic frameworks（MOFs）composed of metal ions and organic ligands have received widespread attention in the construction of new functional materials due to their diverse structure and composition.Therefore,we choose new functional materials MOFs as substrates to customize fluorescent materials for organic pollution analysis.Lanthanide based metal organic frameworks materials not only haveπconjugates of organic ligands,but also have luminescent properties of lanthanide ions.They have unique advantages in selective recognition and detection of organic substances,such as good optical stability,long luminescence lifetime,and high quantum efficiency,greatly expanding their application value.Currently,it is widely used in fields such as chemical sensing,gas adsorption and separation,catalysis,magnetism,and biological imaging.This paper uses different ligands and lanthanide metal ions to construct multiple MOFs materials,and characterizes and analyzes their structures.Their excellent fluorescence characteristics are used to detect pollutants in water.The main work is as follows:（1）Four isomorphic lanthanide metal organic framework complexes,Ln-MOFs:[La₆（BDT）₄（COOH）₂（H₂O）₁₁]_n（1）,[Ce₃（BDT）₂（COOH）（H₂O）₅]_n（2）,[Pr₃（BDT）₂（COOH）（H₂O）₅]_n（3）,[Nd₃（BDT）₂（COOH）（H₂O）₅]_n（4）,and they were subjected to CCD single crystal diffraction,infrared,XRD,thermogravimetry,elemental analysis,N₂adsorption structural characterization such as fluorescence performance and physical and chemical performance testing,crystal data results show that the four complexes belong to monoclinic system,with a spatial group of C2/m,indicating that they are isomorphic complexes.However,through fluorescence comparison in aqueous solution,it was found that complex 2 has good stability and excellent luminescence performance in aqueous solution;This complex has special recognition ability for cation Fe³⁺and drug molecule ciprofloxacin hydrochloride（CIP）,making it a highly sensitive and selective fluorescent probe.The detection limits are Fe³⁺（4.59μmol/L）and CIP（0.77μmol/L）,And further explored the mechanism of fluorescence quenching and fluorescence enhancement.（2）A luminescent lanthanide bimetallic organic framework complex[Tb₆Pr₄（DBA）₆（OH）₄（H₂O）₅·（H₃O）₄]_n（5）containing Tb and Pr coexisting bimetallic elements was successfully constructed using flexible pentacarboxylic acid ligands3,5-bis（2’,4’dicarboxyphenyl）benzoic acid（H₅DBA）,terbium nitrate hexahydrate（Tb（NO₃）₃·6H₂O）,and praseodymium chloride hexahydrate（Pr Cl₃·6H₂O）using solvothermal method.A series of characterization tests were conducted on the complex,such as CCD single crystal diffraction,thermogravimetric analysis,X-ray powder diffraction,infrared,elemental analysis,SEM,energy spectrum,and solid-state fluorescence,indicating that it has good thermal stability and high phase purity.Fluorescence analysis shows that complex 5 can serve as a fast response,high sensitivity,and good selectivity fluorescence sensor for detecting inorganic ions Mn O₄^-and Fe³⁺.（3）Two different bimetallic complexes（[Dy Na（BDT）（H₂O）₃·2H₂O]_n（6）and[Ho Na（BDT）（H₂O）₃·2H₂O]_n（7））,And structural characterization and performance testing were conducted on the two complexes,including CCD crystal diffraction,powder diffraction,thermogravimetric analysis,infrared spectroscopy,elemental analysis and solid-state fluorescence analysis.The comparison showed that complex 6had excellent fluorescence performance and could be used for efficient detection of cysteine（Cys）and acetic acid molecules.The fluorescence quenching mechanism was effectively discussed.In addition,the magnetic properties of the complex were also studied.and it was found that the complex was antiferromagnetism.