Metal-organic frameworks (MOFs) are crystalline systems that can be described as innite networks resulting from the bonding of metal ions, which act as coordination centers, with polyfunctional organic molecules. First prepared by Tomic (1965) and Yaghi et al. (1996), MOFs can be regarded as coordination polymer “sponges” by virtue of their large surface area, high porosity, and permeability to guest molecules (Kitagawa et al., 2004; Rowsell and Taghi, 2005). Remarkably, and in contrast with other microporous materials, there is a lack of any volume inaccessible to guest molecules or ions. Organic linkers contain carboxylate, cyanide, or pyridine coordinating groups. A schematic representation of the Cu(bpy)(H2O)2(BF4)2(bpy) MOF (Jiang et al., 2008) is shown in Figure 5.1.