According to IUPAC, microporous materials have pore diameters of less than 2 nm and macroporous materials have pore diameters of greater than 50 nm; the mesoporous category thus lies in the middle. Microporous materials, especially zeolite have been well studied in the past 20 years, while meso- and macro- structured non-silicate oxides, due to their potential application in the field of catalysis, sensing, adsorptions, energy conversion, and biotechnology, have been the recent subject of much interest.~(2,3) The discovery of M41S silica has stimulated the search for other ordered mesostructured materials with non-siliceous compositions over the last decade. Comparing to silica based compounds for which the chemistry is relatively simple, there are additional challenges for the synthesis of transition metal oxides (TMOs), which are much more reactive than silica-based analogues; uncontrolled condensation yields macroscopic phase segregation.~3 Much effort has been intensively made to synthesize ordered or disordered TMOs using supramolecular surfactants, which have chemically bonded hydrophobic and hydrophilic components on the nanoscale, an assisted 'soft template' pathway based on the self-assembly mechanism.~(4,5) Upon removal of the organic template, ordered mesopores commensurate in size with the template are left throughout the material.~6For the preparation of macroporous TMOs, it is well known that the major technique is the "hard template" method;~7 including templating using ordered colloidal crystal, emulsion, polymer with rod-coil structure, ice, water bubbler and even bacteria.~(8-11) So far, the most applied and successful template would be the colloidal particles, typically silica or polymer, such as polystyrene spheres.~2 Depending on the choice of the inorganic sources and template removal method, different single metal oxides can be readily obtained.~(12) However, this strategy has limitation for the preparation of mixed metal oxides (MMOs) because of the high temperature calcination (usually 900 °C) which is necessary to obtain single phase MMOs with high crystallinity. When polymer spheres are used as the template, the metal precursors pyrolyze at a temperature where the template polymer melts and, therefore, do not form the ordered structure, leading to the collapse of the macroporous framework during the subsequent high temperature
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