Design, Synthesis And Properties Of A New Type Of Nanoscale Rare Earth MOFs

Metal-organic frameworks(MOFs) or porous coordination polymers(PCPs), is a kind of materials with orderly network structure connected by some kinds of chemical bonds between metal ions or metal-based points and organic ligands linkers. As a new kind of organic-inorganic hybrid materials, MOFs can be endowed with the characteristics of high specific surface area, adjustable pore size and easy functionalization, leading to the broad applications in hydrogen storage materials, adsorption, catalysis, and sensing and other fields.In this dessertation, we synthesized a series of nanoscale rare earth metal organic frameworks by using a ionic liquids-assisted hydrothermal method. And we investigated their applications in adsorption and fluorescence sensor.The main contents are as follows: 1. Novel lanthanide-containing metal-organic framework(MOF) nanorods, [C4mim][Cl]-Eu-MOF, [C8mim][Cl]-Eu-MOF and [C12mim][Cl]-Eu-MOF, were conveniently synthesized using ionic liquids-assisted hydrothermal method and characterized by powder X-ray diffraction(XRD), infrared spectroscopy(IR) and transmission electron microscopy(TEM). Interestingly, this ionic liquid-mediated simple and practical method can usefully control the crystal structure and morphology of MOF nanorods without changing other synthetic conditions. In the presence of different ratio of Eu3+: [C4mim][Cl] IL(mol : mol =1:5, 1:10, 1:15), MOF nanorods with the average diameter of 105~ 309 nm can be formed(length : diameter = 7~11). In addition, the obtained nanorods were found to be highly efficient for the removal of congo red(CR) anionic dye from aqueous solutions and the influences of MOF dose, time, pH, CR concentration on adsorption were systematically investigated. [C4mim][Cl]-Eu-MOF exhibited an ultrahigh adsorption capacity of 2606 mg g-1 toward CR under the optimum conditions. Notably, the prominent adsorption efficiency of [C4mim]Cl-Eu-MOF for CR via nanoscale stacking can be directly demonstrated with TEM. In-depth understanding of CR removal using [C4mim]Cl-Eu-MOF nanorods was also supported by FT-IR, Raman, and zeta potential analysis. Utilizing the adsorption kinetic model to fit the experimental data: the results corresponded well with the pseudo-second-order kinectic model.2. Nanoscale rare earth organic framework [C4mim][Cl]-Eu-NMOF with high fluorescence quantum yield was synthesized using ionic liquids-assisted hydrothermal method and applied to the detection of different metal cations and solvent molecules. The results suggested that [C4mim][Cl]-Eu-NMOF can detect the Cu2+ sensitively, the lowest detectable concentration was 1.0×10-7 M.3. Three nanoscale rare earth organic frameworks, [C4mim][Cl]-Eu-MOF, [C8mim][Cl]-Eu-MOF and [C12mim][Cl]-Eu-MOF, were conveniently synthesized using different alkyl chain length of ionic liquids as soft templete for the hydrothermal method and characterized by transmission electron microscopy(TEM). The results showed that these materials could be presented with different morphologies(diameter, length and ratio of length to diameter). At the same time, we detected organic molecules and found that the difference among the corresponding fluorescence analysis limit of detection(LOD) is more than ten times during the sensing of the similiar organic molecules.