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Layered double hydroxides (LDH) comprise an unusual class of layered materials with positively charged layers and weakly bound, often exchangeable, charge-balancing anions located in the interlayer region. This is unusual in solid state chemistry: many more materials have negatively charged layers and cations in the interlayer spaces.〔Evans, David G.; Slade, Robert C. T. "Structural aspects of layered double hydroxides" Structure and Bonding 2006, vol. 119, 1-87.〕 Examples include clay mineral silicates such as kaolinite. LDH's are of interest for their intercalation properties.〔Khan, Aamir I.; O'Hare, Dermot "Intercalation chemistry of layered double hydroxides: recent developments and applications" Journal of Materials Chemistry (2002), 12(11), 3191-3198. 〕 LDHs are commonly represented by the formula ((OH)2 )q+(Xn−)q/n·''y''H2O. Most commonly, z = 2, and M2+ = Ca2+, Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+ or Zn2+; hence q = x. Fixed-composition phases have been shown to exist over the range 0.2 ≤ x ≤ 0.33. However, phases with variable x hare also known, and in some cases, x > 0.5.〔(IMA Nomenclature Report )〕 Examples are also known with z = 1, where M+ = Li+ and M3+ = Al3+. In this case, q = 2x - 1. The latter family of materials can be described by the formula ()X∙''y''H2O (LiAl2-X)). X represents a generic anion and the value of ''y'' is normally found to be between 0.5 – 4. LDHs may be formed with a wide variety of anions X (e.g. Cl−, Br−, NO3−, CO32−, SO42− and SeO42−). ==Applications== The anions located in the interlayer regions can be replaced easily, in general. A wide variety of anions may be incorporated, ranging from simple inorganic anions (e.g. CO32−) through organic anions (e.g. benzoate, succinate) to complex biomolecules, including DNA. This has led to an intense interest in the use of LDH intercalates for advanced applications. Drug molecules such as ibuprofen may be intercalated; the resulting nanocomposites have potential for use in controlled release systems, which could reduce the frequency of doses of medication needed to treat a disorder. Further effort has been expended on the intercalation of agrochemicals, such as the chlorophenoxyacetates, and important organic synthons, such as terephthalate and nitrophenols. Agrochemical intercalates are of interest because of the potential to use LDHs to remove agrochemicals from polluted water, reducing the likelihood of eutrophication. LDHs exhibit shape-selective intercalation properties. For instance, treating LiAl2-Cl with a 50:50 mixture of terephthalate (1,4-benzenedicarboxylate) and phthalate (1,2-benzenedicarboxylate) results in intercalation of the 1,4-isomer with almost 100% preference. The selective intercalation of ions such as benzenedicarboxylates and nitrophenols has importance because these are produced in isomeric mixtures from crude oil residues, and it is often desirable to isolate a single form, for instance in the production of polymers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「layered double hydroxides」の詳細全文を読む スポンサード リンク
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