Syntheses Of Lanthanide Metal-Organic Framework Materials And Their Applications In Fluorescence Sensing

In a growing number of highly porous material categories,metal-organic frameworks?MOFs?are unparalleled in terms of tunability and structural diversity,as well as chemical and physical properties.MOFs are a spatially-extending crystal structure that relies mainly on metal cations or cation clusters to be connected by multi-body organic"pillars"or"linker"ions or molecules.Different structural models of various metal ions and organic connectors provide countless combinations for the crystal structure of MOFs.MOFs have many excellent properties,especially their large surface area and high porosity.The metal-organic framework with fluorescence is a type of MOFs sensor that has been studied extensively by scientists so far,and some good fluorescence spectrum detection methods based on MOFs materials have been established,and their detection limits can also reach trace levels.Lanthanide metal ions mostly have their own characteristic emission spectra,and their luminescence can usually be sensitized by the organic ligand.In this paper,two lanthanide metals are used as metal sources to investigate the synthesis of metal-organic framework materials.The structural characteristics of the product and the application of several metal-organic framework materials in the detection of heavy metal ions in fluorescence are studied.A lanthanide-based metal-organic framework material?Tb-MOF?was prepared by hydrothermal synthesis with lanthanide metal rhenium as the metal source,pyridine-3,5-dicarboxylic acid,and 1,10-o-phenanthroline as ligands.By comparing the PXRD?powder X-ray diffraction?of the material with the PXRD of the crystal structure simulation,the single phase of the compound was determined,and its chemical stability and thermal stability were tested separately.Fluorescence test results show that Tb-MOF has good fluorescence properties in aqueous solution.At the same time,both Fe³⁺and NO₂^-can quench the fluorescence of Tb-MOF.Based on this,the fluorescence sensing of Fe³⁺and NO₂^-in aqueous solution was established.In the concentration range of 2.0-70?M Fe³⁺,the value of I₀/I-1?I₀ and I represent the fluorescence intensity before and after the addition of detection ion?and Fe³⁺showed a good linearity,which the correlation coefficient?R²?was 0.995,and the detection limit was 1.62?M.In the concentration range of 4.0-200?M NO₂^-,the value of I₀/I-1and NO₂^-showed a good linearity with R² and detection limit were 0.994 and 3.4?M,respectively.Finally,this fluorescence sensing method was successfully applied to the detection of Fe³⁺and NO₂^-in several actual water samples.For Fe³⁺,the recovery of the sample in various water samples is 98.86-105.04%,and the relative standard deviation is 0.86-3.88%;for NO₂^-,the recovery is 98.86-105.04%,and the relative standard deviation?RSD?is 0.86-3.88%,respectively.Eu-BTC metal-organic framework material?Eu-BTC MOF?was prepared by hydrothermal synthesis using rhenium nitrate hexahydrate as the metal source and H3BTC?trimesic acid?as the ligand;at the same time,carbon dots?CDs?were synthesized by literature methods.The obtained Eu-BTC MOF and CDs combined to successfully synthesized CDs@Eu-BTC.Infrared and PXRD characterizations proved the successful synthesis of the material.The fluorescence test results showed that the introduction of CDs enhanced the fluorescence of Eu-BTC.The material is used in metal ion sensing experiments.The heavy metal ion Pb²⁺can further increase the fluorescence properties of the material,while other ions do not have this phenomenon.Based on this,a heavy metal Pb²⁺fluorescence sensor was constructed.According to experimental results,CDs@Eu-BTC was linear in the range of 20-100?M,the correlation coefficient R² was 0.998,and the detection limit was 4.12?M for the detection of Pb²⁺.Finally,the material was used to detect Pb²⁺in several actual water samples.The results showed that the recovery and RSD ranged from 99.05%to108.28%and 1.02%to 2.63%,respectively.A lanthanide-based metal-organic framework material?Eu-MOF?was synthesized by hydrothermal method using lanthanide metal rhenium as a metal source,pyridine-3,5-dicarboxylic acid and 1,10-o-phenanthroline as ligands.XRD characterization verified that the synthesized material was a pure phase.The fluorescence intensity of this material in different solvents was investigated.The result shows that the material had most the same fluorescence intensity in the most solvents,such as tetrahydrofuran,toluene,acetonitrile and dichloromethane.However,its fluorescence intensity was completely been quenched once the acetone added.In addition,in the testing of metal ions,we found that the heavy metal Cu²⁺can cause fluorescence quenching.Based on this,the detection of Cu²⁺using acetonitrile as a solvent was established,with a linear range between 6.67-163.93?M,a detection limit of 2.01?M and R² was 0.991.The recoveries in several actual water samples ranged from 99.81%to 116.88%.