Modification And Applications Of Metal-Organic Frameworks With Nano-Sized Channels

In the field of porous materials, metal-organic frameworks are one of the most recent’apples of the eye’. Nanoporous MOFs are highly crystalline inorganic-organic hybrids, and they are constructed by assembling metal ion or metal-containing clusters known as secondary building units (SBUs) with multidentate organic ligands (such as carboxylates, sulfonates) via coordination bonds into a three-dimensional structure. MOFs have attracted considerable attention over the last decade due to their various pore channels and topologies, low density, high surface areas, facile preparation, and flexible tailoring can be systematically tuned by changing the combination of organic ligands and metal ions, such that designer frameworks with exceptional properties for application in gas storage, heterogeneous catalysis, sensing and drug delivery are becoming commonplace. The porosity of MOFs has been shown to be suitable for embedding and supporting activates nanoparticles much higher than traditional zeolite materials. Due to tuneable dimensionality and chemical tailoring of the inner surface of the channels, MOFs can be as a promising new class of templates for hosting nanoparticles compared with microporous zeolites materials. In recently, the embedding of active nanoparticles inside the cavities of MOFs has attracted much attention.In this paper, MOFs were used as carrier for incorporation of active materials such as nanocopper particles, and POMs in order to enhance activity. And we study their corresponding physical and chemical properties. Meanwhile, nanoscale magnetic porous materials were obtained through the calcination of Fe-containing MOF that designed and synthesized and study their magnetic separation and targeted drug delivery. The main of this thesis as follows:1. MIL-101(Cr) synthesized by hydrothermal method was used as carrier for incorporation of copper nanoparticles. Copper nanocrystals were rapid nucleation within the pores of MIL-101(Cr) by hydrazine reduction under microwave irradiation. The result reveals that both small Cu NPs with diameter of2-3nm and Cu NPs with average diameter of100nm are formed, and the small Cu NPs are embedded in the cavities of MIL-101(Cr). The obtained Cu/MIL-101(Cr) nanocomposites showed highly enhanced catalytic activity for the reduction of aromatic nitro compounds. The size of copper nanoparticles that synthesized under the same conditions was10nm, indicated that the growth of the copper nanocrystals inside the pores is limited by the size of the pores. The result reveals high catalytic activity of the Cu/MIL-101(Cr) nanocomposites in comparison pure Cu NPs and MIL-101(Cr) under the same conditions. And the pure MIL-101(Cr) has no catalytic activity under the same conditions. Such an enhancement of catalytic activity may be attributed to the small Cu NPs with a size of2-3nm embedded in MIL-101(Cr), rather than Cu NPs formed around the MIL-101(Cr) crystals. Cheap copper have more development prospects and commercial potential compared with noble metal such as gold, silver, platinum in the catalytic field.2. MIL-100(Fe)noF was synthezed by hydrothermal method in the absence of HF, and takes it as a carrier loaded phosphotungstic acid. The encapsulation of phosphotungstic acid in the MIL-100(Fe)noF has been achieved under two methods. One is impregnation method, the other is one-pot synthesis. The later is encapsulation of phosphotungstic acid within MIL-100(Fe)noF has been achieved by direct hydrothermal synthesis MIL-100(Fe)noF in the presence of phosphotungstic acid. The structures, morphologies, and size of the synthesized samples were investigated by PXRD, IR, SEM and TEM. MIL-100(Fe)noF was synthesized in the absence of HF, leads to poorly crystalline solids that can be confirmed by XRD. However, this method took short time, and avoids use of corrosive acid, and beneficial to the environment. The low phosphotungstic acid encapsulation loading was obtained by impregnation method; meanwhile, the size of the windows of MIL-100(Fe)noF will prevent adsorption within the pores and allow adsorption of phosphotungstic acid only at the external surface of the particles. However, MIL-100(Fe)noF was depredated, under the acidic of the phosphotungstic acid solution. POMs encapsulated by direct synthesis loaded within the pores of MIL-100(Fe)noF; and the dispersion of the phosphotungstic acid is very homogeneous; the concentration of tungsten is very high. The stability tests indicates that the phosphotungstic acid encapsulated by direct synthesis inside the cages of MIL-100(Fe)noF are stable, in agreement with the size of the windows being smaller than those of the phosphotungstic acid. MIL-100(Fe)noF loaded with phosphotungstic acid still exhibits much high BET surface area and pore volume, so small gas molecules can diffuse inside the cavities. We will continue to conduct research its application in catalysis, adsorption and so on.3. MIL-53(Fe) nanocrystals that present narrow size distribution and identical octahedral shape were rapidly synthetized by a microwave-assisted method. The as-synthesized MIL-53(Fe) nanocrystals were then coated with silica as a shell via a sol-gel process. Finally, magnetic porous core-shell nanoparticles were achieved through the calcination of the silica-coated MIL-53(Fe) nanocrystals. The obtained magnetic porous core-shell material exhibited good magnetic characteristic therefore can be easily magnetic separation. Meanwhile, we investigated its loaded nimesulide and slow release property. Up to o.101g g-1, could be adsorbed in the nanocomposite, and it took as long as19d to the complete drug release in physiological saline at37℃. The obtained magnetic pore-core materials can be utilized in a variety of applications, such as magnetic resonance imaging, targeted drug delivery.