The Synthesis,Properties And Application Of Rare Earth Metal-Organic Frameworks Based On Quinoline Derivative Ligands

Metal-Organic Frameworks(MOFs)are constructed from inorganic metal ions/clusters(known as secondary building units,SBUs)and organic ligands through the coordination bonding.Because of the various functions of organic ligands and metal centers,the new types of inorganic-organic framework materials have wide applications in gas storage,separation,sensing,catalysis,drug delivery,nonlinear optics,lasing,and data storage.Owing to their excellent performance in luminescence,electricity,magnetism and catalysis property,Lanthanide metal—organic frameworks(Ln-MOFs)have got much attention in the past few decades.The combination of organic ligands and lanthanide ions can obtain diverse geometric patterns and remarkable physical and chemical properties by synergistic effect.The fluorescence probe based on lanthanide elements usually has a larger stokes shift,which is helpful to reduce the interference from the excitation light and improve the sensitivity and selectivity.Nowadays,a quite number of lanthanide MOFs have been developed,but most of them could not maintain the integrity of their crystal structure in water,which limit their applications in aqueous solution systems.The peroxide mimetic enzymes with high activity in the physiological p H range are rarely reported,and their principles and applications need to be further explored.In this thesis,quinoline derivative 4,4'-(quinolone-5,8-diyl)-benzoate(QBA)was synthesized by using 5,8-dibromoquinoline as the matrix molecule.For their unique electron-donating ability and photochemical properties,we choose Eu³⁺,Tb³⁺,Ce³⁺as the metal center to coordinate with QBA ligands to synthesize three MOFs,named QBA-Eu,QBA-Tb,QBA-Ce respectively.Furthermore,their applications in packaging,adsorption and separation,fluorescence detection have been studied.The relationship between structure and properties of these MOFs have been investigated.These results will help to provide a theoretical basis for the novel multifunctional MOFs.The main results are as follows:1.A three-dimensional layered MOFs(named QBA-Eu)was synthesized by using Eu(?)and 4,4'-(quinolone-5,8-diyl)-benzoate(QBA)ligands as raw materials in solvothermal reaction.Due to the competitive coordination between the metal nodes and organic ligands and water molecules,the reversible phase transition from three to two dimensions QBA-Eu in aqueous and organic solvents was realized,and the reversible phase transition was proved by scanning electron microscopy,transmission electron microscopy,atomic force microscopy,powder X-ray diffraction and photoelectron spectroscopy.Using the unique property,dye molecules that could not be encapsulated in MOFs can be encapsulated into MOFs.2.QBA-Eu nanobelts had abundant carboxyl sites exposed to the outside.Based on the coordination between Fe³⁺and carboxyl group,QBA-Eu nanobelts can be used as a new adsorbent for the adsorption and removal of Fe³⁺in aqueous solution.It was found that Fe³⁺was adsorbed on QBA-Eu nanobelts surface in the form ofa-Fe₂O₃ through coordination with free carboxyl groups,and the adsorption did not destroy the structure of QBA-Eu nanobelts by using scanning electron microscopy(SEM),transmission electron microscopy(TEM),powder X-ray diffraction(PXRD)and X-ray photoelectron spectroscopy(XPS).After optimizing the adsorption conditions,the adsorption capacity of QBA-Eu nanobelts for Fe³⁺is as high as 465.0mg/g,which is superior to many reported adsorbents for Fe³⁺.Hence,QBA-Eu nanobelts have a good application as an adsorbent for practical samples such as Fe³⁺in Lake water.3.Fluorescence spectra show that the transfer energy happened between QBA and Eu(?)in QBA-Eu nanobelts,that is,QBA can sensitize central ion Eu(?).Therefore,the fluorescence of ligand QBA and Eu(?)can be observed in the aqueous solution of QBA-Eu nanobelts.However,the coordination ability of QBA with Eu(?)decreases due to the coordination between PO₄^3-and Eu(?)in QBA-Eu nanobelts after adding PO₄^3-in solution,which further increases the fluorescence of QBA in QBA-Eu nanobelts(l_em=410 nm)and decreases the fluorescence of Eu(?)(l_em=620 nm).Based on that phenomenon,the fluorescence ratio of QBA-Eu nanobelts at 410 and 620 nm was used to determine the PO₄^3-in the system.The results show that the method possessed good regeneration,stability and practicability.The detection showed a linear response to phosphate salts in the range of 10.0?90.0mM with the detection limit of 6.1×10^-6 mol/L.This method has realized the detection of phosphate salts in human serum samples and recoveries in the range of 98.93%¹07.3%.4.QBA-Tb was synthesized by solvothermal reaction using Tb(NO₃)₃ and QBA ligand.Then structure and morphology of QBA-Tb were characterized,and interaction between QBA-Tb and pyridine-2,6-dicarboxylic acid(DPA)was studied.The results show that the interaction between DPA and QBA-Tb does not change the composition and structure of QBA-Tb,but sensitizes the Tb(?)and makes the new fluorescence peaks of QBA-Tb appear at 490 and 545nm.Based on the relationship between fluorescence intensity of QBA-Tb at 545 nm and DPA concentration,a fluorescence spectrometry method for DPA determination was established.The detection method showed a linear response to DPA in the range of 0.1?300.0mM with the detection limit of 1.6×10^-8mol/L(13)When used to detect real water samples,it obtained satisfactory results.5.Aggregation induced luminescence(AIE)molecule(HDBB)was encapsulated into QBA-Tb nanochannels by host-guest encapsulation,and the AIE behavior of HDBB molecule was studied in this confined space.The results show that the fluorescence of HDBB@QBA-Tb at 570 nm is hardly affected by the p H and solvent of the system,but can be selectively quenched by Fe³⁺.Based on the phenomenon,a highly selective fluorescence quenching method for the determination of Fe³⁺was established.The detection method showed a linear response to Fe³⁺in the range of(15)(13)(16)²⁴(15)m(44)with the detection limit of 6.3×10^-8 mol/L,the recoveries ranged from 99.4%to 107.3%,and the relative standard deviation(RSD)was less than 4.0%.6.QBA-Ce was synthesized by using Ce(NO₃)₃ and QBA ligands as raw materials in solvothermal reaction.The structure and morphology of QBA-Ce were characterized,and its catalytic performance was studied.We found that QBA-Ce have the high activity of hydrogen peroxide mimetic enzymes under physiological p H conditions,and can be used as an efficient peroxidase.Based on the unique property,QBA-Ce as an efficient catalase mimetic enzyme could be used to detect glucose in drugs.This method showed a linear response to glucose in the range of 1.0×10^-5?2×10^-3 M with the detection limit of 5.4×10^-6 mol/L(13)The recoveries ranged from 106.5%to 98.0%,and the relative standard deviation(RSD)was less than 2.5%.Therefore,QBA-Ce as peroxidase mimetic enzymes have potential application in medical diagnosis and biotechnology.