Design And Application Of Luminescent Materials Based On Metal-Organic Frameworks (MOFs) In Sensing And Anti-counterfeiting

Metal-organic frameworks（MOFs）are a kind of porous crystal materials with spatial network structure formed by self-assembly of metal ions and organic ligands through coordination bonds.They have the advantages of special topological structure,adjustable pore size,large specific surface area,great thermal and chemical stability,meanwhile,and MOFs with multifunctional properties can be obtained by changing the types of metal ions and organic ligands.In this paper,two novel Zn-MOFs were synthesized by using different carboxyl ligands,and the fluorescence of MOFs was regulated by introducing guest luminescence groups and combining with other luminescent materials,and then their fluorescence characteristics under different stimuli were investigated respectively.The main research contents and results are as follows:（1）The composite material BT@HPU-20 of bentonite（BT）and HPU-20 was obtained by solvothermal method.Using the obtained composites as carriers,Tb³⁺and Eu³⁺ions with different molar ratios were encapsulated into the composites,thereby obtaining Ln³⁺@BT@HPU-20 fluorescent composites with characteristic emission of Tb³⁺and Eu³⁺.The composite Ln³⁺@BT@HPU-20 can achieve sensitive detection of bacillus anthracis biomarkers（DPA）and PO₄^3-through different fluorescence effects.Meanwhile,the RGB value of the fluorescent probe solution can be collected by a smartphone,and it is substituted into the detection limit formula,which can also realize semi-quantitative visual detection of DPA or PO₄^3-.（2）Three-dimensional framework material HPU-22 was obtained by solvothermal method using anthracene carboxylic acid ligands.The study of the fluorescence properties showed that the blue fluorescent of HPU-22 transformed into cyan fluorescent of HPU-22H200 after being heated at 200°C.In addition,HPU-22H200also can change its fluorescence color by simple solvent wetting,and recovered its own cyan fluorescence after drying.Mechanistic studies show that the sample heated at200°C causes a slight shrinkage change in the distance between adjacent anthracyclines,resulting in a change in fluorescence color.We take advantage of the thermal stimulus-responsive fluorescent properties of materials and apply them to the field of fluorescent anti-counterfeiting,which will provide a new method to improve the level of anti-counterfeiting.（3）A new composite material CsPbBr₃@HPU-22 was prepared by vacuum drying method,using HPU-22 as a carrier to encapsulate CsPbBr₃ in channels.The obtained composite material has high sensitivity to water.Under the stimulation of humid environment or water vapor,CsPbBr₃@HPU-22 can be seen from yellow powder to white powder,and accompanied by a change in fluorescence,which recovers after drying to achieve a reversible color change.In addition,the CsPbBr₃@HPU-22exhibited high sensitivity to acid-base gases,accompanied by a change in fluorescence color under UV light.The material can be applied to the field of fluorescent anti-counterfeiting thanks to its multi-stimulus response characteristics.The fluorescence change response to water stimulation and acid-base gas stimulation may provide new ideas for future anti-counterfeiting research.