Metal-oxide frameworks

Mesoporous materials with a transition metal oxide framework have immense potential for applications in catalysis, photocatalysis, sensors, and electrode materials because of their characteristic catalytic, optical, and electronic properties. However, for some applications, this potential can only be maximized in the highly crystalline... 

It is not expected to be significant because of the three-dimensional metal oxide framework (see Figure 6.32), and not a layered structure as was always the case in the three previous examples. Yet the obvious anisotropy of the crystallite shapes (see the inset in Figure 6.31) suggests that the possibility of a complex preferred orientation cannot be completely excluded. 

Molecular hydrogen storage in metal oxide frameworks... 

M.l. Khan, M. I. E.Yohannes, and D. Powell, Synthesis and characterization of a new mixed-metal-oxide framework material composed of vanadium oxide clusters x-ray crystal structure of (N2H5)2[Zn3V, V 6042(S04)(H20)i2]-24H,0 J. Chem. Soc., Chem. Com.,13 (1999). (b) M. I. Khan. 

Fig. 3.3 The single crystal X-ray structures of zeohtic imidazolate metal-oxide frameworks (MOFs). In each row, the net is shown as a stick diagram (left) and as a tiling center). The largest cage in each MOF is shown with ZnN tetrahedra in blue (right). H atoms are omitted for clarity ...

Generally, there are three preparative methods for synthesizing polymer/metal oxide nanocomposites (Fig. 1). The first is direct mixing or blending of a polymer and metal oxide NPs, either as discrete phases (known as melt mixing) or in solution (solution mixing). The second is a sol-gel process, which starts with a molecular precursor at ambient temperature and then forms a metal oxide framework by hydrolysis and condensation. The third is in-situ polymerization of monomers in the presence of metal oxide NPs. 

It is first important to classify the different types of nanostructures and their relevant characteristics and morphological features at the nanoscale, according to their dimensionality, as illustrated in Fig. 4.1. One can clearly distinguish OD nanostructures with nanoparticles, clusters and mesoporous systems as MOFs (Metal Oxide Frameworks), ID nanostmctures with nanotubes and nanowires, 2D nanostructures with multilayers and 3D nanostructures with nanostructured and nanocrystalline materials. In this context, nanocrystalline materials are defined as single- or multi-phase polycrystaUine solids with a grain size of a few nanometres... 

The sol-gel technique has attracted enormous interest over 3 decades in the area of material science because this method facilitates the preparation of novel materials that are based on metal-oxide clusters. This process begins with molecular precursor at ambient temperature and then forms a metal or metal-oxide framework by hydrolysis and condensation. The formation of interpenetrating networks between inorganic and organic moieties at a milder temperature improves compatibility and builds strong interfacial interactions between two phases. This process has been used successfully to prepare different nanocomposites (Mallakpour and Dinari, 2012). 

It has long been recognized that lithium can be inserted chemically into metal oxide frameworks. Both molybdenum oxides [87, 88] and vanadium oxides [89] were synthesized for this purpose. The reversibility of insertion reaction in these alkali... 

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