Topochemical Oxidation of Transition Metals in Layered Double Hydroxides by Anthraquinone-2-sulfonate

Layered double hydroxides (LDH), also known as hydro-talcite-like clays, consist of positively charged metal hydr-oxides and charge balancing anions, expressed by a general formula [M2+(1-x)M3+x(OH)2]An−x/n·mH2O, wherein M2+ and M3+ can be any divalent and trivalent metal cations occupied in the octahedral holes of a brucite-like layer and An − is any hydrated exchangeable anion positioned in the gallery bet-ween the layers through a strong electrostatic and intermole-cular interaction.1 Physical and chemical properties of the LDHs could be tuned by changing the composition of the LDH host layers such as transition metals e.g. Co, Ni, Fe etc. for catalysts, electrochemical materials and magnetic pre-cursory materials.2 Especially, Fe3+ readily formed a gel-like Fe(OH)3 phase in an alkaline solution3 and Fe2+-Fe3+ LDHs (green rust) could be obtained by an oxidation of brucite-lik