Synthesis of layered double hydroxide anionic clays intercalated by carboxylate anions

Layered double hydroxides (LDHs) containing carboxylate anions are often contaminated with carbonate or other anions arising from atmospheric carbon dioxide or precursor salts, respectively. If the structure of the layered host is to be exploited in order to control features such as the stereochemistry of reactions of intercalated guest species or the kinetics of their ion-exchange, or if the structure of the host–guest assembly is to be compared with molecular dynamics simulations it is essential to prepare materials containing the target anion only. In this paper, we show that LDHs containing citrate, oxalate, tartrate and malate ions free from other anions may be obtained by a simple procedure involving dissolution of a magnesium–aluminium, nickel–aluminium or zinc–aluminium carbonate-containing LDH precursor by addition of the appropriate carboxylic acid followed by precipitation of the product by addition of the mixture to a basic solution. In contrast to other synthetic procedures for LDHs, the reaction does not need to be carried out under nitrogen in order to prevent co-intercalation of carbonate ions.