Research On The Synthesis And Application Of Several Lanthanide Metal-organic Frameworks In Analytical Chemistry

Metal-Organic Frameworks(MOFs)are a type of porous crystalline materials which is constructed from metal ions(or metal clusters)and organic ligands by coordination bonds.Due to the wide tunability of their composition and structure,MOFs show great application potential in the fields of gas storage and separation,catalysis,biomedicine,proton conduction,magnetic materials and luminescent materials.The lanthanide metal-organic frameworks materials(Ln-MOFs)constructed with lanthanide metal ions as the central ions have excellent luminescence performance,which is due to the large Stokes shift,long luminescence Lifetime and narrow emission half-width,it can reduce the interference from the excitation light to improve the sensitivity of detection.These advantages make it unique in the field of analytical chemistry.However,most of the Ln-MOFs have poor stability in water and fluorescence will be quenched to some extent in water and complex synthesis methods.These shortcomings limit their further application in aqueous solution detection systems.This paper designed and synthesized three types of Ln-MOFs,using single crystal X-ray diffraction,powder X-ray diffraction,infrared,thermogravimetric and other characterization methods to carry out structural analysis of them.The research content of this thesis is mainly divided into the following three parts:1.5,8-dibromoisoquinoline was selected as the matrix molecule to synthesize quinoline derivative 4,4'-(isoquinoline-5,8-diyl)-benzoate,named iQBA.Due to its unique optical properties,we select europium(?)ions as the metal center and iQBA as the ligand to obtain a three dimensional layered Ln-MOFs(named Eu-iQBA)through solvothermal reaction.The structure and morphology were characterized by single crystal X-ray diffraction,infrared,scanning electron microscopy and transmission electron microscopy.At the same time,the water stability and fluorescence properties were studied.Studies have shown that the fluorescent properties are different under acidic and alkaline conditions,and in the range of p H 3.0-7.0,the logarithm of the fluorescence intensity ratio of Eu-iQBA at 465 nm(emission of ligand)and 619 nm(emission of Eu³⁺)is linear with p H.2.In order to get better water stability Ln-MOFs,this paper choses1,5-pentanedioic acid as the organic ligand,terbium(?)ion as the metal center to synthesize a Ln-MOFs(named Tb-PTA)by liquid-assisted grinding,the structure was characterized by single crystal structure analysis,ts stability and luminescence properties were studied.The research results show that Tb-PTA have good water stability and can produce a specific response with DPA.Based on the relationship between the fluorescence intensity of Tb-PTA at 547 nm and the concentration of DPA,a fluorescence spectroscopy method for the determination of DPA was established,the detection range is 1 nM-10?M and the detection limit is 0.81 nM.3.Using europium(?)ion and terbium(?)ion as the metal center,oxalyl dihydrazide as the ligand,we synthesize three kinds of Ln-MOFs by stirring method in aqueous solution at room temperature(named Eu-ODZ,Tb-ODZ and Eu/Tb-ODZ).Their stability and fluorescence properties were studied.The results show that the series of Ln-MOFs have good stability in aqueous solution.After adding a certain amount of DPA,the fluorescence color of Eu/Tb-ODZ aqueous dispersion changes from orange to green.The ratio detection method can be established by measuring the ratio of the intensity at 547 nm and 619 nm which has a linear range of 1 nM to 1000 nM with a detection limit of 0.34 nM.