Synthesis and spectroscopic 27Al NMR and Raman characterization of new materials based on the assembly of [AlO4Al12(OH)24(H2O)12] 7þ isopolycation and Co–Cr and [AlMo6O24H6] 3- Anderson heteropolyanions

Abstract

New advanced inorganic composite materials were prepared by combination of the polycation [AlO4Al12(OH)24(H2O)12]7+ with heteropolyoxomolybdates of Anderson type structure with formula: [XMo6O24H6]3- where X=Al(III), Co(III), and Cr(III). The synthesis of these materials is performed by direct mixture of the isopolycation and heteropolyanions in a pH controlled aqueous solution. These new materials were characterized by X-ray powder diffraction (XRD), 27Al nuclear magnetic resonance (NMR); vibrational (FT-IR and Raman Microprobe) and UV–visible diffuse reflectance (UV–vis-DR) spectroscopies and their stability was studied by thermal analysis (TG-DTA). The NMR and Raman spectroscopies are useful to characterize these materials and to demonstrate that the Anderson structure in the composite lattice is preserved. Likewise, XRD, Raman microprobe and UV–vis-DR spectroscopic techniques achieve the further characterization of thermal residues or intermediates. All results allow us to suggest that the evolution of properties depends on the heteroatom nature in the Anderson structural units of these new materials.