Controlled Synthesis And Adsorption Property Of Porous Coordination Polymer Nano/micromaterials

Over the past few years, studies on porous coordination polymers (PCPs) have been rapidly developed owing to their varying framework structures, high stability, tailored pore structures, high surface areas and specific properties. Recently, not only the abundant chemical compositions and structures, but also the small size and specific morphology dependent properties make porous coordination polymer nano/micromaterials more attractive for the applications in some specific fields compared with bulk coordination polymers. In addition, although the chemical composition and structure of PCPs nano/micromaterials determine their properties, it was found that the applications of PCPs nano/micromaterials also depend on their crystal morphology and size. Therefore, controlled synthesis of porous coordination polymer nano/micromaterials with specific morphology and size is attractive, however, remains a great challenge.In this thesis, three organic ligands, namely benzene-1,3,5-tricarboxylic acid (H3BTC),4,4’,4"-benzene-1,3,5-triyl-tribenzoic acid (H3BTB),1,4-di(1H-imidazol-4-yl)benzene (H2L), were used to react with metal salts to give PCPs nano/micromaterials with controllable morphology and size under different reaction conditions. All the complexes were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and so on. The crystal formation mechanism of PCPs nano/micromaterials and the influences of crystal shape and size on adsorption properties were studied in detail. There are six main parts in this thesis:1.[Cu3(BTC)2](HKUST-1) nano/microstructures were successfully synthesized via direct precipitation method in the ethanol-water mixed solvent at room temperature using BTC3-triethylammonium salt and Cu(NO3)2-3H2O as the reactants and cetyltrimethylammonium bromide (CTAB) as the surfactant. With increasing concentration of CTAB, an evolution of particle morphology is observed:from cube, truncated cube, cuboctahedron, truncated octahedron to octahedron. At the same time, the particle size is found to increase simultaneously. In addition, the concentration of the reactant is another important factor for determining the particle size and morphology of [Cu3(BTC)2] products. Gas sorption measurements indicate that the cubic [Cu3(BTC)2] products prepared without CTAB have the highest amount of nitrogen adsorption and BET surface area, and the decrease of crystal size induces the increase in the crystal surface area.2. HKUST-1nano/microstructures were successfully synthesized via direct precipitation method in the ethanol-water mixed solvent at room temperature using BTC3-triethylammonium salt and Cu(NO3)2·3H2O as the reactants and neutral inorganic salts as the additives. The addition of inorganic salts could determine the morphology and size of HKUST-1, and Na+and K+stabilizes{111} facets of HKUST-1at different levels. The gas adsorption properties of HKUST-1with different shapes were studied and the results reveal that the porous coordination polymer microcrystals display morphology dependent sorption property.3.[Cu3(BTB2)](MOF-14) crystallites were successfully obtained via direct precipitation method at room temperature using H3BTB and Cu(NO3)2·3H2O as the reactants in the ethanol-water mixed solvent. The amount of sodium acetate added into the reaction, which increases the supersaturation of crystal growth and results in the formation of crystals with high-energy crystal facets, plays a crucial role in the shape evolution of MOF-14from rhombic dodecahedron to truncated rhombic dodecahedron and cube with truncated edges and then to cube. The morphological evolution is also observed for HKUST-1from octahedron to cube, which verifies the probable mechanism of morphological transformation. The gas adsorption properties of MOF-14with different shapes were studied and the results reveal that the porous coordination polymer microcrystals display morphology dependent sorption property.4.[Eu(BTB)](MIL-103) nanocrystals with controllable morphology and size were successfully synthesized via direct precipitation method at room temperature using H3BTB and Eu(NO3)3·6H2O as the reactants in the ethanol-water mixed solvent. With increasing the amount of sodium acetate, the particle morphology of MIL-103changes from microrods to nanonods and finally to nanoparticles. Gas sorption measurements indicate that MIL-103nanorods have the highest amount of nitrogen adsorption and BET surface area, and also show excellent performance for the separation of CO2/N2mixture. In addition, due to the characteristic photoluminescence, MIL-103nanorods could be used for sensing molecules, and the results imply that MIL-103nanorod is a high sensitive and selective sensor for Cu(II) ions and acetone molecules in solution.5. MOF-14crystallites were successfully synthesized through a solvothermal process using H3BTB and Cu(NO3)2·3H2O as the reactants. Coordination modulator of acetic acid, pH adjusters of sodium acetate and surfactant of polyvinylpyrrolidone (PVP) were added in the reaction system respectively to prepare MOF-14with different morphology and size. The gas adsorption properties of MOF-14with different shapes were studied and the results reveal that the MOF-14microcrystals display morphology and size dependent sorption property, and MOF-14nanocrystals synthesized with sodium acetate also show mesoporous distribution.6. Ellipsoid-like [Cu(L)] nanocrystals were successfully synthesized via an ultrasonic-assisted solution-phase method at room temperature using H2L and Cu(NO3)2·3H2O as the reactants. Aqueous ammonia in the reaction system not only can deprotonate ligand H2L, but also can coordinate with Cu(II) and act as a coordination modulator to affect the nucleation rate of the [Cu(L)] product to form larger size particles. The N2, CO2, CH4, H2adsorption properties and adsorption selectivity for CO2over N2have been investigated, indicating that nanosized [Cu(L)] shows a better adsorption performance than bulk [Cu(L)] and can serve as a potential H2storage material.