Design,Synthesis And Properties Of Novel MOFs Used For Photoluminescence And Fluorescence Switch

Metal-organic frameworks?MOFs?have attracted great interest because of their unique porous structures,synthetic advantages,organic-inorganic hybrid nature,and versatile applications.By designing the conformation and coordination mode of organic ligands and the coordination geometry of metal centers,it is possible to make its structure adjustable and flexible,and even to obtain functional materials with new physical and chemical properties,by exploring MOFs as carriers for loading functional organic compounds.In this paper,designed to study the application of photoresponsive molecular switches of metal organic frameworks,especially photochromic and fluorescent switches,eight photo-induced MOFs in the application of molecular switch materials were designed and fabricated by both self-assembly synthesis and pore loading.The specific research contents are as follows:This paper includes three parts as follows:?1?Under the solvothermal conditions,[Zn?COO??1,4-bpeb?_0.5?2-NH₂-bdc?_0.5]_n?MOF-1?was synthesized by self-assembly with the mixture of 1,4-bis[2-?4-pyridyl?ethenyl]-benzene?1,4-bpeb?,2-aminoterephthalic acid?2-NH₂-bdc?and metal ion Zn II,showing photo-induced fluorescent switches.MOF-1 exhibits two-fold interpenetration3 D framwork,with the distance between the double bonds in parallel-arranged paired1,4-bpeb ligands that allows to undergo photoactivity [2+2] cycloaddition.After UV irradiation,it was accompanied by a single-crystal-to-singlecrystal?SCSC?transformation with a framework topology change from CdS net to {6²·8³·10}{6⁵·8}₂ net.The resulting phase is defined as [Zn?COO?R_0.5?2-NH₂-bdc?_0.5]_n?MOF-2?,containing light-induced product tetragonal ring?R?.In addition,the polymer MOF-2 was heated at60 °C for 6 hours to undergo a reversible thermo-cleavage,and then original material MOF-1 was obtained again.This reversible structure transition of cycloaddition/cleavage results in their superior application as reversible photo/thermo-switchable dual-color green-to-blue fluorescence molecules.?2?Under the solvothermal conditions,[Zn?L??bpdc?·solvents]?MOF-3?was synthesized by self-assembly with the mixture of the N-diarylethylene derivatives?L?organic ligands,4,4'-biphenyldicarboxylic acid?H₂bpdc?and metal Zn?.The three-dimensional porous MOF-3 exhibits a dia net with a porosity of about 36.9% and a pore size of 8.4×10.8?².In this material,the photoresponsive diarylethene diarylethene unit undergoes an exquisite change triggered by UV and visible light between open-ring and closed-ring isomers,so that MOF-3 underwent a fast photochromic reaction with colour switching between buff and dark blue,and photofluorescence switch with fluorescent trun off/on.?3?Using the rotary evaporation method,the porous MOF [Zn?L??bpdc?] was used as the carrier to load chromophore organic compounds?anthracene,phenanthrene,fluorene,pyrene,phenanthroline and 2,2'-bipyridine?,consequently tend to do the generation of MOF@chromophore series materials were prepared,respectively namely MOF@anthracene,MOF@phenanthrene,MOF@fluorene,MOF@pyrene,MOF@phenanthroline and MOF@2,2'-bipyridyl.Due to it is photoresponsive diarylethene diarylethene unit was maintained in MOF@Chromophore series materials,the change triggered by UV and visible light between open-ring and closed-ring isomers results in MOF@Chromophore series materials not only have the photochromic properties?buff/dark blue?,also the performance of the photofluorescence switch.