hydrotalcitelike

Hydrotalcite-like materials, often written as hydrotalcite-like or hydrotalcitelike, are a family of layered double hydroxides (LDHs) that resemble brucite structure but carry positive sheet charges balanced by interlayer anions and water. They consist of positively charged metal hydroxide layers formed by partial substitution of divalent cations with trivalent cations, creating a charge that is neutralized by interlayer species.

The general chemical formulation is [M2+1-x M3+x (OH)2]x+ (A^n-)x/n • mH2O, where M2+ and M3+ are divalent and trivalent cations (for example Mg2+, Al3+, Zn2+, Fe3+), x is the fraction of trivalent cations, and A^n- is an interlayer anion such as CO3^2-, NO3^-, Cl^-, SO4^2-, or various organic anions. The Mg–Al system is common, typically with Mg/Al ratios around 2:1 to 3:1, producing a layered nanoscale structure with tunable composition.

Synthesis typically involves co-precipitation of metal salts at controlled pH, often followed by aging and sometimes hydrothermal treatment. Key properties include high anion exchange capacity, basic sites, and the ability to intercalate a wide range of inorganic and organic species. Their structure allows reversible deintercalation/intercalation of interlayer anions, enabling tailored functionalities.

Upon calcination around 450–550 °C, hydrotalcitelike materials decompose to mixed metal oxides with high surface area and basic character. These derived oxides function as catalysts, adsorbents, and catalyst supports, and can be rehydrated to re-form LDH phases.

Applications span environmental remediation, catalysis (base-catalyzed reactions and biomass transformations), flame retardancy, polymer composites, and drug delivery through intercalation of therapeutic agents.