a process is provided for the preparation of a metallic oxide composite including mixing an aqueous solution of a water - soluble metal compound and colloidal silica , depositing the mixture upon a substrate , heating the mixture - coated substrates at temperatures from about 150 ° c . to about 300 ° c . for time sufficient to form a metallic oxide film , and , removing the silica from the metallic oxide film whereby a porous metal oxide structure is formed .