Layered double hydroxides basic structure

Constantino V. R. L. and Pinnavaia, T. J. Structure-reactivity relationships for basic catalysts derived from a Mg21 /Al31 /CO32 layered double hydroxide, Catal. Lett., 1994, 23, 361-67. 

Cr3+ can also be integrated into the structures of layered double hydroxides. A mixed oxide, prepared by calcination of ZnCr-LDH-CCh, was used in combination with t-BuOOH for the ketonization of alkyl and of benzyl pyridines and for the oxidation of benzyl amines to give Schiff bases (67,68). In contrast to MgAl-LDHs, for example, these materials display hardly any basicity so that base-catalyzed side reactions such as aldol condensations are avoided. 

The layered double hydroxides have been of interest as anion exchangers, basic catalysts, and catalyst precursors. Pillared derivatives of the type discussed earlier for the clays have been synthesized by ion exchange with polyoxometallate anions but have lower thermal stability. Several authors have reported synthesis of layered double hydroxides pillared with the Vio028 ion by direct ion exchange or by techniques that involve preswelling the layer structure with an organic anion. For example, the terephthalate anion was used in the synthesis ofVio028 and Mo7 024 intercalated phases. 

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