Block Copolymer-Assisted Synthesis of Mesoporous, Multicomponent Oxides by Nonhydrolytic, Thermolytic Decomposition of Molecular Precursors in Nonpolar Media

Abstract

A general route for the synthesis of homogeneous mixed-element oxides, based on the use of block polyalkylene oxide copolymers and single-source molecular precursors, is described. Thermolytic decomposition of the molecular precursors in the presence of an anhydrous solution of the block copolymer (in toluene) led to monolithic gels. The polymeric structure-directing agent was then removed by calcination at 500 °C for 3 h under O2. The generality of this synthetic approach is demonstrated with the molecular precursors Zr[OSi(OtBu)3]4, (EtO)2Ta[OSi(OtBu)3]3, Fe[OSi(OtBu)3]3·THF and [Al(OiPr)2O2P(OtBu)2]4, which have been converted to the corresponding mesostructured materials ZrO2·4SiO2, Ta2O5·6SiO2, Fe2O3·6SiO2, and AlPO4 (denoted UCB1-ZrSi, UCB1-TaSi, UCB1-FeSi, and UCB1-AlP, respectively). These mesostructured materials, characterized by TEM, XRD, N2 porosimetry, EDX, and NMR spectroscopy, exhibit wormholelike pore structures, high surface areas, and narrow pore size distributions.