Construction Of New Type Rare Earth MOFs And Its Sensing Properties Research

With the rapid development of society,the easily enriched inorganic ions,volatile organic molecules and phenols cause certain pollution to the environment,which seriously affects the survival and health of human beings,and the safety of water body has attracted more and more attention.How to detect water pollutants quickly,with high sensitivity and low detection limit is very important.Among the many detection methods,fluorescence detection is especially favored for its unique advantages.In traditional inorganic fluorescent materials,rare earth elements occupy an important position.Since the MOF was proposed in 1995,more and more scholars have studied the introduction of rare earth ions into metal-organic framework materials to form new luminescent materials.Due to the easy enrichment of crystals,the design of the structure,and the unique fluorescence properties of rare earth ions,it is expected to use the change in fluorescence intensity of rare earth ions as an indicator to qualitatively and quantitatively detect pollutants in water bodies.In this paper,gadolinium chloride hexahydrate（GdCl₃·6H₂O）and3,5-di（2’,4’-dicarboxylphenyl）benozoic acid（H₅DBA）are used as raw materials to successfully fabricate three-dimensional porous rare earth MOFs（Gd-MOF）materials by hydrothermal method under slightly alkaline conditions,The molecular formula of the Gd-MOF characterized by single crystal X-ray diffraction was[Gd₁₀（L）₆（OH）₄（H₂O）₃]·4H₃O（1）.The structure of the MOF is centered on Gd³⁺binuclear and tetranuclear,where the binuclear metal is alternately connected by H₅DBA to form a dual-line one-dimensional chain and two-dimensional plane,and then expands into a three-dimensional microporous MOF material with Gd³⁺as the core.The micropores are occupied by the formation of tetranuclear by Gd³⁺and hydroxyl oxygen,which enhances the stability of the Gd-MOF.Then it was characterized by thermogravimetric（TGA）,Infrared Radiation（IR）,elemental analysis,Energy Dispersive Spectrometer（EDS）,powder X-ray diffraction（PXRD）and solid fluorescence analysis.Characterization analysis shows that the Gd-MOF has a complete structure,good thermal stability,high phase purity,and good fluorescence performance.Research on the fluorescence of Gd-MOF shows that the prepared Gd-MOF can detect Fe³⁺,Cr₂O₇^2-and H₂O₂ with high sensitivity,at the same time,it can detect trinitrophenol in water by using the unique electrochemicalproperties of Gd-MOF.Complex 1 has the characteristics of low dosage,fast analysis speed,high sensitivity,good selectivity,simple operation and real-time detection,which enriches the application of new luminescent MOFs materials formed by rare earth elements in substance detection.In the buffer reagent（acetic acid/sodium acetate）with p H=6,Using terbium nitrate hexahydrate（Tb（NO₃）₃·6H₂O）and a flexible organic ligand H₄BDT as raw materials,a new three-dimensional material Tb（Na）-MOF by hydrothermal method,the molecular formula is Na Tb（BDT）·5（H₂O）（2）.It was Characterized by single crystal X-ray diffraction,elemental,thermogravimetric,Infrared Radiation,X powder-ray diffraction and solid fluorescence.Analysis of single crystal X-ray diffraction data revealed that Na⁺coordinated with N and O in the ligand,and Tb³⁺coordinated with O in the ligand,and the ligands were alternately connected to form a heteronuclear three-dimensional structure.Through other characterization,it was found that Tb（Na）-MOF had good thermal stability,high phase purity and excellent fluorescence performance.The Tb（Na）-MOF can detect environmental pollutants Fe³⁺,Cr₂O₇^2-and acetaldehyde molecules with high sensitivity and selectivity.At the same time,it has good electrochemical activity and can detect catechol（CC）in water.The high sensitivity,high selectivity and low detection limit of complex 2 will be used in the detection of pollutants in water.On the basis of the study of complex 1,the use of terbium nitrate hexahydrate（Tb（NO₃）₃·6H₂O）,Europium nitrates hexahydrate（Eu（NO₃）₃·6H₂O）and flexible pentanoic acid organic ligands（3,5-di（2’,4’-dicarboxylphenyl）benzoic acid,H₅DBA）were used as raw materials to successfully construct a novel three-dimensional material Eu（Tb）-MOF in which Eu and Tb coexist（3）.It was Characterized by single crystal X-ray diffraction,thermogravimetric（TGA）,Infrared Radiation（IR）,Energy dispersive spectrometer（EDS）,X powder-ray diffraction（PXRD）and solid fluorescence analysis.Characterization analysis shows that the Eu（Tb）-MOF has a complete structure,good thermal stability,high phase purity,and good fluorescence performance.The fluorescence performance showed that the constructed Eu（Tb）-MOF could detect chloroform（CHCl₃）and Cr₂O₇^2-with high selectivity,high sensitivity and low detection limit,and can also be used for electrochemically sensitive detection of phenol.Eu（Tb）-MOF has high selectivity,high sensitivity and low detection limit and other characteristics will become a sensing material for detecting environmental pollutants.