Synthesis and characterization of terephthalate-intercalated NiAl layered double hydroxides with high Al content

Abstract

Terephthalate-intercalated nickel–aluminum layered double hydroxides (LDHs) were prepared by a co-precipitation method, with nominal x values in the general formula Ni_(1−x)Al_x(OH)₂(C₈H₄O₄)_x/2 in the range 0.3–0.8. The materials were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, CHN analysis, thermogravimetric analysis, FTIR spectroscopy, EXAFS at the Ni edge and ²⁷Al NMR spectroscopy. A combination of XRD, XRF and CHN analysis indicated that crystalline LDHs with true x values up to 0.5 were obtained, along with increasing segregation of an aluminum hydroxide phase with increasing aluminum content. The EXAFS analysis indicated an upper limit of ca. 0.6 for the atomic fraction of aluminum at the second nickel coordination sphere. The ²⁷Al NMR analysis suggested that a phase containing octahedrally co-ordinated Al³⁺ is segregated for nominal x values from 0.6 upwards.