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.