Heterobimetallic sol–gel precursors and intermediates

Abstract

The question how the metals in bimetallic sol–gel materials are positioned relative to each other and how the dispersion of the metals can be controlled is a major preparative and analytical challenge. Two particular aspects are addressed: The first is an alternative type of single-source precursors where the two metals are interlinked through an organic spacer. The new options provided by this approach are demonstrated for metal oxide/silica nanocomposites, zinc titanate and Co3O4/ceria catalysts. The second issue with regard to heterobimetallic systems is the kind of intermediates formed during sol–gel co-processing of two different metal precursors (metal alkoxides or metal alkoxide + metal salt). Systematic investigation of the structures of Ti/M oxo clusters (M = main group or transition metal, or lanthanide) shows some interesting common construction principles and thus sheds light on early stages of the structural evolution in mixed-metal oxide systems.