Controlled Synthesis And Properties Of Nano/Microscale Metal-Organic Framework Materials

In the past two decades, porous metal-organic frameworks (MOFs) have attracted considerable scientific interest not only because of their intriguing varieties of compositions and structures, but also due to their potential applications in gas adsorption, storage and separation, catalysis, drug delivery and so on. The small size and specific morphology-dependent properties make MOF nano/micromaterials more attractive for the applications in some specific fields compared with bulk MOFs. In addition, although the chemical composition and structure of MOF nano/micromaterials determine their properties, it was found that the applications of MOF nano/micromaterials are closely related with their crystal morphology and size. Therefore, the shape and size control of MOFs are important to develop new nanomaterials with enhanced performances or unique applications, however, it is still challenging.In this thesis, three ligands, namely benzene-1,4-dicarboxylic acid (H2BDC), 2-aminoterephthalic acid (H2N-BDC) and biphenyl-3,4’,5-tricarboxylic acid (H3BHTC), were used to react with metal salts to give five MOF nano/micromaterials. All the complexes were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and so on. The formation mechanism of MOF nano/micromaterials and the influences of crystal shape and size on adsorption properties were studied in detail. There are five main parts in this thesis:1. Ni(Ⅱ)-doped MOF-5 nano/microcrystals with controllable morphology and size were successfully obtained by solvothermal method using H2BDC, Ni(NO3)2·6H2O and Zn(NO3)2-6H2O as the reactants in the ethanol and N,N-dimethylformamide (DMF) mixed solvent. In the presence of C2H5OH, crystal size and shape can be well tailored upon variation of the volume ratio of C2H5OH:DMF, resulted in cubic and truncated octahedral crystals with different sizes. In addition, the reactant concentration is another important factor for determining the particle size and morphology of Ni(Ⅱ)-doped MOF-5. By changing reactant concentration, truncated cubic and cubic crystals with different sizes were obtained. Gas sorption measurements indicate that the sorption profiles of the Ni(ⅡI)-doped MOF-5 nano/microcrystals are dependent on the morphology and size of the particles.2. Co(Ⅱ)-doped MOF-5 nano/microcrystals with controllable morphology and size were successfully obtained by solvothermal method using H2BDC, Co(NO3)2·6H2O and Zn(NO3)2·6H2O as reactants, acetic acid (HAc) as coordination modulator in the ethanol-DMF mixed solvent. The morphology of samples was well tailored upon the addition of HAc modulator to the reaction mixture, resulted in cubic and cuboctahedral crystals with different sizes. In addition, the reaction temperature is important for the generation of particles and manipulation of their size. The gas sorption measurements reveal that the cubic Co(Ⅱ)-doped MOF-5 products have the high amount of nitrogen and carbon dioxide adsorption and large Langmuir surface area. Co(Ⅱ)-doped MOF-5 nano/microcrystals not only significantly enhance structural stability of MOFs towards moisture, but also act as a new type of sensing materials for recognition of solvent molecules.3. IRMOF-3 nano/microcrystals with controllable morphology and size were successfully obtained by simple solvothermal method using H2N-BDC and Zn(NO3)2·6H2O as the reactants and cetyltrimethylammonium bromide (CTAB) as the surfactant in the ethanol-DMF mixed solvent. The shape evolution of IRMOF-3 crystals from cube, to truncated cube, cuboctahedron, truncated octahedron and finally to octahedron was achieved by adjusting the amount of CTAB. In addition, the surface microstructure of the IRMOF-3 nano/microstructures is affected by reaction temperature. Gas sorption measurements indicate that the cubic IRMOF-3 products prepared without CTAB have the highest amount of nitrogen and carbon dioxide adsorption and BET surface area, the gas sorption properties of IRMOF-3 crystals were found to be dependent on the morphology of particles.4. UMCM-150 nanostructures with controllable morphology and size were successfully obtained by a facile and rapid method using H3BHTC and Cu(N03)2·3H2O as the reactants, and triethylamine (TEA) as modulator in the ethanol-H2O-DMF mixed solvent at room temperature. The morphology of as-prepared samples was well tailored upon the addition of TEA to the reaction mixture, resulted in the formation of uniform hierarchical flower-like and net-like UMCM-150 nanostructures. The as-obtained samples were used as adsorbents in waste-water treatment, and showed very good ability to rapidly remove methylene blue.5. Porous ZnO and ZnO-NiO composite nano/microspheres have been successfully synthesized by calcination of non-doped and Ni(Ⅱ)-doped coordination polymer precursors in air, respectively. The catalytic effect was investigated for porous ZnO and ZnO-NiO composite nano/microspheres on the thermal decomposition of ammonium perchlorate (AP). The ZnO-NiO composite nano/microspheres showed remarkable catalytic effect for the thermal decomposition of AP. The decomposition temperature was decreased by 144.5℃ and the apparent activation energy was significantly decreased to 117.8 kJ mol’1, which is considerably lower than 159.7 kJ mol’1 for pure AP. In addition, using the as-prepared porous ZnO microspheres, we have successfully prepared a novel, ultrahigh resolution electrochemical impedance DNA biosensor for the enhanced detection of the PML-RARA fusion gene in acute promyelocytic leukemia with the detection limit of 2.2 × 10-13 mol L"1.