ABSTRACT
Layered double hydroxides (LDHs) are host-guest materials consisting of positively charged metal hydroxide sheets with intercalated anions and water molecules, called anionic clay minerals [1]. They can be represented by a general formula, [M2+1-xM3+x(OH)2]x+ An−x/n yH2O, where M2+ and M3+ are divalent and trivalent metal cations, such as Mg2+, Zn2+, Ca2+, etc., and Al3+, Co3+, Fe3+, respectively, An− are interlayer anions, such as CO32−, Cl−, and NO3−. The anions occupy the interlayer region of these layered crystalline materials. The most commonly known naturally occurring LDH clay is hydrotalcite (Mg-Al type) with the chemical formula Mg6Al2(OH)16CO30.4H2O, showing a structure represented in Figure 8.1.
