General Synthesis of Periodic Macroporous Solids by Templated Salt Precipitation and Chemical Conversion

This paper presents a general method to prepare three-dimensionally ordered macroporous (3DOM) metal oxides or carbonates via templating with polystyrene (PS) spheres. The method is based on templated precipitation of metal salts (acetates, oxalates, oxides) within a colloidal crystal of PS spheres and subsequent chemical conversion of the inorganic precursors. The compositional range of possible macroporous products includes oxides or carbonates of many metals in the periodic table (e.g., MgO, Cr₂O₃, Mn₂O₃, Fe₂O₃, Co₃O₄, NiO, ZnO, CaCO₃), including compositions that are less accessible or more expensive by previous syntheses based on metal alkoxide precursors. Optimal synthesis conditions and structural features of selected materials are described, based on XRD, TGA, SEM, TEM, nitrogen adsorption data, and chemical analysis. These novel macroporous dielectric or semiconducting materials are expected to be of interest in applications such as catalysts, supports, sensors, wave guides, and porous electrodes or electrolytes.