Construction And Fluorescence Properties Sduty Of Lanthanide Functionalized Metal-Organic Frameworks Materials

In the era of industrial and economic globalization,human health assessment and information security are particularly important.To meet the sustainable development of ecological systems,there is a need to enhance the prevention and monitoring of environmental pollution so as to effectively improve human health.In addition,information leakage and counterfeit goods have penetrated almost every industry related to human security.In view of the above issues,there is a growing interest in the development and innovation in the field of environmental monitoring and anti-counterfeiting technologies.Porous functional materials can combine various components with different physical and chemical properties to achieve cross-fertilization of various disciplinary frontiers.Metal-organic frameworks（MOFs）are a type of organic-inorganic hybrid porous material that self-assembles by organic ligands and inorganic metal ions/metal clusters under particular conditions.MOFs are a promising choice for generating and growing multifunctional hybrid materials with unique features because to their inherent advantages of organic ligands and inorganic metal ions,tunable porosity,and varied functional sites.Among them,the natural luminescence properties of lanthanide ions(Ln³⁺ions)combined with the structural properties of MOFs provide a good choice for the design of novel photofunctional MOFs composites.The introduction of photoactive Ln³⁺ions can lead to unique luminescent properties of lanthanide functionalized MOFs materials,which are widely used in optical fields such as chemical sensing,fluorescence modulation,anti-counterfeiting and bioimaging.Oriented design and effective synthesis of lanthanide functionalized MOFs based on application requirements is an important challenge for the construction of porous functional materials,and also the only way to realize their practical application.Based on this,based on environmental monitoring and optical anti-counterfeiting,thisthesis constructs lanthanide functionalized MOFs fluorescent composites with two different paths:Ln-MOFs with Ln³⁺ions as metal nodes and Ln@MOFs with Ln³⁺ions as guests.The relationship between the structure and properties of lanthanide functionalized MOFs was explored from the perspectives of environmental science,materials science and analytical chemistry.The details of the research are as follows.1.Ln-MOF（HNU-48）with one-dimensional channels was synthesized under solventhermal reaction of Eu（NO₃）₃ and 1,1,2,2-tetra（4-carboxyphenyl）ethylene（H₄TCPE）ligand.Rhodamine B（Rh B）was introduced into HNU-48 to prepare Rh B@HNU-48composites.It has been shown that Rh B@HNU-48 has dual-emission fluorescence corresponding to the characteristic emission of Rh B and H₄TCPE.Rh B@HNU-48 exhibited a sensitive dual-emission fluorescence response to alachlor with an ultra-low detection limit of 0.59 ppb,and was able to provide accurate monitoring of pesticides in the actual environment.Based on the highly sensitive sensing performance of Rh B@HNU-48,a fluorescent logic gate operation instruction was designed to achieve the evaluation of different alachlor concentration ranges.2.Ln-MOF（HNU-49）with one-dimensional channels was synthesized under solventhermal conditions using Tb（NO₃）₃ and H₄TCPE ligand.Because the H₄TCPE ligand contains four aromatic rotors（benzene rings）with highly distorted structures,HNU-49 has the property of piezofluorochromic behavior.With the change of pressure,the fluorescence color of HNU-49 can achieve a reversible change from blue to green.Rhodamine B（Rh B）can be encapsulated in the channels to prepare Rh B@HNU-49 composites.Rh B@HNU-49not only possesses the dual-emission corresponding to the characteristic emission of Rh B and H₄TCPE,but also maintains the piezofluorochromic property of HNU-49.By precisely controlling the Rh B concentration and the applied pressure,Rh B@HNU-49 can exhibit a variety of fluorescence emission and even near-white emission.Based on this,Rh B@HNU-49 can be further used to make colored LED devices.3.Dual-emission Ln-MOF（HNU-72）with one-dimensional channels was synthesized by Eu（NO₃）₃,Cd（NO₃）₂ and H₄TCPE ligands under solventhermal conditions.Compared with the pre-synthesized HNU-48,the introduction of Cd²⁺ion during the synthesis of HNU-72could successfully induce the dual-emission fluorescence belonging to Eu³⁺ion and H₄TCPE.The energy transfer process between H₄TCPE and Eu³⁺ion in HNU-72 before and after the introduction of Cd²⁺ion was analyzed by DFT theoretical calculations.In addition,HNU-72 with dual-emission fluorescence can achieve ratiometric fluorescence sensing of dimethyl sulfide（DMS）in the ocean with a detection limit of 14 ppb.4.The anionic Ln-MOF（HNU-67）with one-dimensional channels was synthesize d under solvothermal conditions by Tb（NO₃）₃ and 3,5-di（2′,4′-dicarboxylphenyl）benzo ic acid（DBPA）ligand.Considering the porosity of the anionic HNU-67,the SRB@HNU-67 composites were obtained by introducing sulfonated rhodamine B（SRB）in to HNU-67 via ion exchange.A series of dual-emission anti-counterfeiting materials with adjustable fluorescence color can be obtained by adjusting the SRB content an d excitation wavelength in SRB@HNU-67.In addition,SRB@HNU-67 was loaded in polystyrene-methyl methacrylate（PS）arrays to construct SRB@HNU-67/PS comp osites.The composites have synergistic optical properties of angle-dependent structur e color and excitation-dependent fluorescence color,which are uniquely advantageou s for multi-modal anti-counterfeiting and information storage applications.5.MOF（HNU-60）with one-dimensional channels was synthesized under solvothermal conditions using Cd（NO₃）₂ and 1H-tetrazol-5-ylacetic acid（H₂tza）ligand.Considering that the structure of HNU-60 contains reactive groups not involved in coordination,two fluorescent guests(Ln³⁺ions and carbon quantum dots（CDs）)were introduced in situ into HNU-60 to construct a series of Ln³⁺/CDs@HNU-60 composites with multiple fluorescence emission.The organic ligands and CDs in HNU-60 can synergistically sensitize the characteristic fluorescence of Ln³⁺ions,making Ln³⁺/CDs@HNU-60 exhibit excitation-dependent tunable fluorescence.The fluorescence changes of Ln³⁺/CDs@HNU-60 can be achieved by modulating the interactions between HNU-60 to CDs,HNU-60 to Ln³⁺and CDs to Ln³⁺.In the 260-440 nm excitation range,Ln³⁺/CDs@HNU-60 exhibits characteristic fluorescence transition between Ln³⁺ions and CDs.Ln³⁺/CDs@HNU-60 can be used in multi-mode optical anti-counterfeiting due to its fluorescence conversion.