Construction Of New Metal-organic Frame Materials (MOFs) And Their Application In Environmental Detection

Metal-organic frameworks（MOFs）is a one-dimensional,two-dimensional or three-dimensional extension structure formed by organic ligands with multiple bonding sites combining metal ions or metal clusters self-assembly in the form of coordination bonds.It has a unique pore topology.The high specific surface area,as well as the availability of internal pore functions and external surface modifications,make them potentially useful for gas storage/separation,drug diversity,catalysis,proton conduction,sensing,etc.Luminescent MOFs have made great progress in synthesis,design and sensing applications in recent years,and have attracted the attention of many researchers as an ideal sensing material.In this paper,a novel luminescent MOFs were constructed from the two aspects of ligand and metal,and the fluorescence generated by the interaction between rare earth elements,organic ligand and guest molecules was studied.This excellent fluorescence property was applied to the detection of environmental pollutants.The main work contents are as follows:（1）Using 6-（4’-carboxyphenyl）pyridinic acid（H₂CPA）and samarium nitrate（Sm（NO₃）₃·6H₂O）hexahydrate,a new type of highly efficient luminescent Sm-MOF containing Sm metal was successfully constructed by hydrothermal method.CCD single crystal X-ray diffractometer,elemental analyzer,thermogravimetric analyzer,X-ray diffractometer,infrared detector and scanning electron microscope were used to characterize the MOF.The results show that Sm-MOF has hexagonal prism morphology and three-dimensional pore structure.Sm-mof has good structural stability and excellent luminescence properties in aqueous solution.Because Bi³⁺and Mn O₄^-had obvious enhancement and quenching effects on Sm-MOF fluorescence,the detection limits were 1.06μmol·L^-1(Bi³⁺)and 4.59μmol·L^-1（Mn O₄^-）,respectively,and the fluorescence quenching mechanism was further discussed.Based on this,a fluorescence detection method for Bi³⁺in water was established.The recovery rate of Bi³⁺in actual water samples was 98%～102%,and the relative standard deviation was 1.54%～3.35%.（2）3,5-bis（2’,4’-dicarboxyphenyl）benzoic acid（H₅DBA）,terbium nitrate（Tb（NO₃）₃·6H₂O）hexahydrate and erbium nitrate（Er（NO₃）₃·6H₂O）hexahydrate were selected to construct a new bimetallic Tb/Er-MOF with high efficiency by hydrothermal method.And a series of characterization results showed that the structure of the material is similar to that of the mononuclear metal-organic skeleton Tb-MOF and Er-MOF.The fluorescence test results show that the Tb/Er-MOF pair can specifically detect H₂O₂,Fe³⁺and Cr₂O₇^2-in water.Detection limits were 8.45μmol·L^-1,0.1123μmol·L^-1,and6.64μmol·L^-1,respectively.And the fluorescence quenching mechanism was discussed respectively.（3）Using 3,5-bis（2’,4’-dicarboxyphenyl）benzoic acid（H₅DBA）,terbium nitrate hexahydrate（Tb（NO₃）₃·6H₂O）and holmium acetate hexahydrate（Ho（Ac）₃·6H₂O）as raw materials,Tb/Ho-MOF heteronuclear bimetallic organic skeleton luminescence materials co-existing with Tb and Ho were successfully constructed by hydrothermal method.Through series characterization,the structure of the complex is similar to that of the mononuclear organometallic skeleton Tb-MOF and Ho-MOF,and has excellent fluorescence properties.The results show that Tb/Ho-MOF has excellent sensing properties for formaldehyde,Fe³⁺and Mn O₄^-in aqueous solutions,and the detection limits are 2.32μmol·L^-1,2.73μmol·L^-1 and 6.83μmol·L^-1,respectively.（4）Using 3,5-bis（2’,4’-dicarboxyphenyl）benzoic acid（H₅DBA）,europium nitrate(Eu（NO₃）_3·6H₂O)and lanthanum nitrate(La（NO₃）_3·6H₂O)as raw materials,a heteronuclear bimetallic organic framework luminescent complex Eu/La-MOF with lanthanide co-existing metals was successfully constructed by hydrothermal method.The structure of the complex is similar to that of Eu-MOF and La-MOF,the mononuclear metal-organic skeleton of the same ligand.Fluorescence sensing studies showed that the complex had excellent sensing properties for acetone molecules,Cu²⁺and H₂PO₄^-in aqueous solutions,with detection limits of 1.91μmol·L^-1,1.31μmol·L^-1 and 0.94μmol·L^-1.