Layered double hydroxides (LDHs) are a class of materials with useful properties associated with their anion exchange abilities for a wide range of materials’ applications including adsorbent, catalyst and its support, ceramic precursor, and drug carrier. In order to satisfy the requirements for the detailed characterization and the practical application, the preparation of LDHs with varied composition and particle morphology has been examined extensively. The versatility of the preparation methods led LDHs with varied composition and micro/macroscopic morphology, which makes the application of LDHs more realistic. In the present review article, synthetic methods of LDHs are overviewed in order to highlight the present status of the LDHs for practical application.

NiFe layered double hydroxides (LDHs) intercalated with dioctyl sulfosuccinate with varied Fe3+/(Ni2+ + Fe3+) ratios (0.04–0.25) were prepared by constant-pH co-precipitation from an aqueous solution of Ni and Fe perchlorates...

Layered double hydroxides (LDHs), shown as the general formula of [M2+1−xM3+x(OH)2]x+(An−)x/n∙yH2O, are useful for various applications such as anion exchangers/adsorbents, catalysts and catalysts’ supports, and drug/gene carriers due to their structural, compositional and morphological characteristics and their variation. The x value (M3+/(M2+ + M3+) ratio) in layered double hydroxides (LDHs), corresponding to the layer charge density, is one of the important parameters for controlling the properties of LDHs. The x values in commonly available LDHs are limited (0.2 < x < 0.3). In order to obtain LDHs with x < 0.2, Mg2+ Ga3+–LDHs with interlayer iodide were examined. The linear correlation between lattice parameter a and x value in the products with x of 0.06–0.24 was seen, suggesting the successful substitution of Mg2+ in the brucite-like sheet with Ga3+. Carbonate and dodecyl sulfate types MgGa–LDH were prepared by ion exchange with carbonate anion and reconstruction in aqueous solution of sodium dodecyl sulfate. The products with x of 0.06 were dispersed in water and hexanol better than those with x of 0.24 for MgGa–LDHs containing carbonate and dodecyl sulfate, respectively, suggesting effects of the lower layer charge density on the dispersion.

Bismuth oxyhalides and layered alkali titanates are promising components to design high-performance hybrid photocatalysts. In this work, a hybrid photocatalyst composed of lepidocrocite-type layered cesium titanate (Cs0.7Ti1.77Li0.23O4, CsTLO) and bismuth oxyiodide (BiOI) was designed rationally based on lattice matching. BiOI formed on the layered titanate by ion exchange of CsTLO with Bi cations and subsequent growth of BiOI nanodisks (6 nm in the thickness and 125 nm in the lateral size) in an aqueous solution of cesium iodide, resulting in the hybrid where BiOI nanodisks were lying flat on the layered titanate and exposed the (001) facet predominantly. The present hybrid exhibited efficient photodegradation of methylene blue (4, 10, and 14 times higher than that of CsTLO, Bi-TLO, and BiOI, respectively), which was ascribed to the efficient charge transfer in the bulk and at the interface assisted by the built-in internal electric fields and the high activity of (001) BiOI for direct oxidation of the pollutant.