Facile preparation of three-dimensionally ordered macroporous alumina, iron oxide, chromium oxide, manganese oxide, and their mixed-metal oxides with high porosity

This paper describes a facile method to produce three-dimensionally ordered macroporous (3DOM) alumina, iron.oxide, manganese oxide, chromium oxide, and their mixed-metal oxides. An ethylene glycol (EG)-methanol mixed solution of metal nitrates was infiltrated into the void of the colloidal crystal template of a monodispersed poly(methyl methacrylate) (PMMA) sphere. Heating initiated nitrate oxidation of the EG to produce metal glyoxylate salt. Further heating converted the glyoxylate salt to metal oxide and decomposed PMMA which produced the desired 3DOM metal oxides. Two important parameters of this method are clarified in order to produce a well-ordered 3DOM structure in high yield: (1) The nitrate oxidation temperature should be lower than the glass transition temperature of the PMMA. (2) The heat produced by oxidative decomposition of the PMMA should effectively be removed. Furthermore, high porosity (66-81%) of the 3DOM materials was confirmed by Hg porosimetry, which can permit facile transport of guest molecules and particles in potential catalysis and filtration.