A Comparative Study of Macroporous Metal Oxides Synthesized via a Unified Approach

A variety of macroporous metal oxides was synthesized via a spontaneous self-assembly process in aqueous solution starting from organic alkoxide precursors under a common set of conditions to present a consistent set of data for evaluation of macropore formation in these materials that are known to yield such structural patterns. Sol-gel-type chemistry appears to be governing the structure formation in these materials, so the influence of sol-gel parameters such as the alkyl group in the alkoxide, the central metal atom, and the pH of the reaction mixture were investigated in order to gain insight on the defining mechanism dictating the formation of these structures. The results revealed that depending upon the central metal atom or the alkyl group, the alkoxide precursors had characteristic hydrolysis and condensation rates, which, when balanced appropriately, resulted in structured macroporous pattern formation in the final materials. Powders obtained in the spontaneous self-assembly processes were found to have varying macropore sizes as well as extents of macroporosity upon adjusting standard sol-gel synthesis parameters, which control the relative rates of the hydrolysis and condensation reactions.