Preparation of three-dimensionally ordered macroporous perovskite-type lanthanum–iron-oxide LaFeO3 with tunable pore diameters: High porosity and photonic property

Three-dimensionally ordered macroporous (3DOM) lanthanum–iron-oxide (LaFeO3) with different pore diameters was prepared using a colloidal crystal of polymer spheres with different diameters as templates. Ethylene glycol–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 of this PMMA–metal salt–ethylene glycol composite produced the desired well-ordered 3DOM LaFeO3 with a high pore fraction, which was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury (Hg) porosimetry, and ultraviolet–visible (UV–vis) diffuse reflectance spectra. 3DOM LaFeO3 with pore diameters of 281 and 321 nm shows opalescent colors because of photonic stop band properties. Catalytic activity of the 3DOM LaFeO3 for combustion of carbon particles was enhanced by a potassium cation, which was involved from K2S2O8 used as a polymerization initiator.