Synthesis of functional zinc layered hydroxide and its organic-inorganic nanohybrids

Zinc layered hydroxide (ZLH) is a family of layered metal hydroxide (LMH) which can be represented by the general formula, M²⁺(OH)²-x(An-)x/n.mH2O, where M²⁺ is the metallic cation (e.g., Mg²⁺, Ni²⁺, Zn²⁺, Ca²⁺, Cd²⁺, Co²⁺, and Cu²⁺) and An- is a counter anion with (n-) charge. ZLH is similar to layered double hydroxide (LDH), in which it is composed of positively charged brucite-like inorganic layers and exchangeable counter anions together with water molecules in the interlayer. ZLH can be prepared using various methods and it was found that polymer such as PVA and PEG can be used as size controlling agent for zinc layered hydroxide and its calcined product. The counter anion can be exchanged with various organic anions, resulting in the formation of various organicintercalated or the so-called layered organicinorganic nanohybrid materials. The intercalated organic moieties can be ion exchanged with other anions in a sustained manner, resulting in a controlled release property. This was proved possible when herbicides such as 4-chlorophenoxyacetate were used as the organic guests. In addition, zinc-layered nanohybrids can also be prepared using structural memory effect using gallate as the guest anion. Thermal decomposition of doped and undoped zinc layered-gallate nanohybrid with Fe3⁺, Co²⁺ and Ni²⁺ can be used as a route for the formation of high pore volume, mesoporous carbon material.