High surface area homogeneous nanocrystalline bimetallic oxides obtained by hydrolysis of bimetallic µ-oxo alkoxides

Abstract

Homogeneously dispersed bimetallic oxides in nanocrystalline or amorphous forms, of the type MAl₂O₄ (where M = Mg, Ca, Mn, Co, Fe, and Zn) were prepared from bimetallic oxo-bridged alkoxides [(RO)₂Al–O–M–O–Al(OR)₂], where the Al–O–M–O–Al bonds were not hydrolytically cleaved. This approach yields hydroxides [(HO)₂Al–O–M–O–Al(OH)₂] which, upon thermal dehydration, yield oxides [OAl–O–M–O–AlO], such that M is homogeneously dispersed with an empirical formula of MAl₂O₄. These materials were obtained in high surface area forms and were characterized by X-ray diffraction, electron microscopy, surface area analyses, and solid-state ²⁷Al NMR. Comparative studies of the hydrolysis of alkoxo-bridged alkoxides yielded mixed metal oxide phases with lower surface areas.