Inorganic Chemistry, Vol.37, No.8, 1812-1820, 1998
Synthesis and characterization of polyoxovanadate-pillared Zn-Al layered double hydroxides : An x-ray absorption and diffraction study
Zn-Al layered double hydroxides (LDHs) have been prepared with Cl- and CO32- interlayer anions and with Zn/Al ratios of 2 and 3. The corresponding polyoxovanadate-containing LDHs were then prepared by anion exchange reaction at different pH values. The products were characterized by atomic absorption, PXRD, FT-IR spectroscopy, TG analysis, and transmission electron microscopy (TEM). Thr resulting vanadate-containing LDHs, depending on the pH and the Zn/Al ratio, consisted of one or more phases. PXRD patterns corresponding to layered compounds with different gallery heights (7.0, 4.6, and 2.6 Angstrom for V10O286-, V4O124- and (VO3)(n)(n-) chains, respectively) were observed. X-ray absorption spectroscopy has been also used to assess the local geometry of vanadium ions in the different samples, and results indicate the presence of V5+ ions in octahedral and/or tetrahedral coordination depending upon the conditions of the synthesis.