Tungsten polyoxometalates

Layered double hydroxides pillared by tungsten polyoxometalates : Synthesis and photocatalytic activity

Abstract

Layered double hydroxides pillared by tungsten polyoxometalates were prepared by anion exchange reaction of the synthetic precursor, Mg4Al2(OH)12TA·H2O, Zn3Cr(OH)8DS·2H2O or Zn2Al(OH)6NO3·H2O with the polyoxometalates. The intercalated polyoxometalates included the Paratungstate A [W7O24]6− ion; the monosubstituted or lacunary Keggin [SiW11O39Mn(H2O)]6−, [SiW11O39Ni(H2O)]6− or [SiW11O39]8− ion; the monosubstituted Dawson [P2W17O61Mn(H2O)]8− ion and the Preyssler [NaP5W30O110]14− ion, resulting in the gallery heights of the intercalates in the range 0.76∼1.70 nm. The photocatalytic activities of the intercalates were studied by the degradation reaction of an aqueous organochlorine pesticide, hexachlorocyclohexane (HCH). The model and mechanism for the photocatalytic degradation of HCH on the polyoxometalate-pillared compounds were proposed, indicating that the interlayer space is the reaction field and that photogeneration of OH· radicals are responsible for the degradation pathway.

Keywords

A. layered double hydroxides; hexachlorocyclohexane; polyoxometalate; B. anion exchange reaction; D. photocatalytic activity