Progress on layered hydrotalcite (HT) materials as potential support and catalytic materials

Mixed metal oxides derived from layered hydrotalcite (HT) materials are extensively used as a potential catalyst and catalytic support in various organic transformations. Numerous such materials have been developed by varying framework divalent and trivalent metal ions, and interlayer anions. The intercalation of anions present in HT facilitates the design of high surface area materials possessing exposed active sites, which enhances the catalytic and adsorption properties. These HT materials have also been used as drug carriers, and in enzyme encapsulation owing to their flexible accommodation of organic anions in the interlayer of the HT structure. The present review is focused on a recent development in the preparation of various HT materials using different metals and intercalating ions and their importance in the various catalytic processes, such as base catalyzed alkylation, isomerization, condensation and esterification. Effectiveness of transition metals containing HT for redox catalytic processes, viz. oxidation of alcohol, alkyl aromatics, phenol and reduction of nitro compounds have been discussed. Further, the importance of the introduction of a hard anion like silicate into the interlayer space of the HT and its applications in various organic reactions has also been covered in this review.