Synthesis And Properties Of Luminescent Lanthanide Metal-Organic Frameworks With Fluorene-based Dicarboxylic Acid Ligands

Over the past two decades, Metal-organic frameworks (MOFs) have been an active research area because of their functional properties and potential applications in materials science which are crystalline materials constructed from metal ions and organic ligands. MOFs have shown promising applications in the areas of gas storage and separation, luminescence, magnetism and catalysis. The cavities or channels in their structures also make MOFs competitive candidates for chemosensors.In this thesis, based on 9-methyl-9-hydroxy-fluorene-2,7-dicarboxylic acid (H2MHFDA) and 9-fluorenone-2,7-dicarboxylic acid (H2FDC), seven highly efficient lanthanoid-based luminescent MOFs materials have been prepared and structurally characterized. These complexes (1-7) were characterized by single crystal X-ray diffaration, powder X-ray diffraction, elemental analysis, infrared spectrum, photoluminescence spectra, thermogravimetric analysis and so on. The applications of these complexes in guest recognition, PA sensing and white light-emission materials have also been investigated. The main contents of this thesis are summarized as follows:1. Based on 9-fluorenone-2,7-dicarboxylic acid and lanthanoid Eu3+/Tb3+ metal ions, two novel MOFs materials have been synthesized under solvothermal condition. The structure of these MOFs are [Tb3(FDC)4(NO3)4](H2O)4((CH3)2NH2+)3 The Tb ions are connected by the carboxylic groups to produce the 1D parallel aligned Tb-O-C rods extending along the [010] direction. The Tb-O-C rods are linked by the 9-fluorenone moieties of the FDC ligands forming the threedimensional rod-packing framework. Both of the two complexes exhibit green luminescence which indicate the weak energy transfer between FDC ligands and lanthanoid ions.2. Based on solvothermal condition, we synthesized a new flexible three-dimensional metal organic framework which is constituted of 9-methyl-9-hydroxy-fluorene-2,7-dicarboxylic acid and lanthanoid Eu3+ metal ions. (Me2NH2)3[Eu3(MHFDA)4(NO3)4(DMF)2]·4H2O·2MeCN. This MOF has a three-dimensional framework structure with one dimensional rhombic channels and the framework can be reversibly transformed between two phases upon release/uptake of the guest molecules. The vacuum drying process is accompanied by the loss of luminescence of the MOF, while the luminescence is recovered upon resoaking in DMF. The potential of the material for PA sensing was studied in DMF through the luminescence quenching experiments, which elucidate that this material is a potential turn-off luminescent sensory material for the selective detection of PA.3. Based on the research of structures and fluorescent properties of the complexes synthesized by 9-fluorenone-2,7-dicarboxylic acid or 9-methyl-9-hydroxy-fluorene-2,7-dicarboxylic acid. A series of three-dimensional complexes which have various fluorescent properties have been synthesized by doping with different ligands and metal ions: (Me2NH2)3[Gd3-yEuy(MHFDA)4-x(FDC)x(NO3)4(DMF)2]·4H2O·2MeCN (0<x<4,0<y<3). A novel white light-emission materials could be synthesized by the variety of doping ratio.