Mesoporous materials have been synthesized that are composed of hybrid frameworks in which inorganic and organic components have a fixed stoichiometry and are covalently bonded. The creation of UOFMN (unified organically functionalized mesoporous networks) materials incorporates concepts employed in the synthesis of MCM-41 mesoporous silicates, making use of a quaternary ammonium cationic surfactant and a double trialkoxysilyl precursor such as bis(triethoxysilyl)ethane (BTSE) or bis(triethoxysilyl)ethylene (BTSEY). The cetyltrimethylammonium (CTA + ) surfactant is removed by extraction with acid, resulting in a high surface area porous organosilicate framework in which Si atoms are bridged by ethane (from BTSE) or ethylene (BTSEY) groups. The channels are wormlike and uniform in diameter. UOFMN materials are more hydrothermally stable than MCM-41 prepared under similar conditions and have thicker pore walls. Ethylene groups in products made with BTSEY can be brominated, the brominated product itself being reactive as a bromide source. The UOFMN products were characterized by XRD, N 2 adsorption, solid-state 29 Si and 13 C NMR, and TEM.

Titania, zirconia, and alumina samples with periodic three-dimensional arrays of macropores were synthesized from the corresponding metal alkoxides, using latex spheres as templates. In a fast, single-step reaction, the monomeric alkoxide precursors permeate the array of bulk polystyrene spheres and condense in air at room temperature. Close packed, open-pore structures with 320- to 360-nanometer voids are obtained after calcination of the organic component at 575 degreesC. The examples presented demonstrate the compositional diversity possible with this technique. The resulting highly structured ceramics could have applications in areas ranging from quantum electronics to photocatalysis to battery materials.

The synthesis of highly ordered macroporous materials has been accomplished in a straightforward, single-step reaction. Inorganic frameworks composed of oxides of Si, Ti, Zr, Al, W, Fe, Sb, and a Zr/Y mixture were formed from metal alkoxide precursors templated around polystyrene (latex) spheres. Monodisperse latex spheres were ordered into closepacked arrays by centrifugation. The interstices between latex spheres were permeated by the alkoxide, which hydrolyzed and condensed. An inorganic framework was formed upon drying. Removal of the latex spheres was accomplished by either calcination at temperatures between 450 and 1000°C or extraction with a tetrahydrofuran/acetone mixture. The resulting products consisted of periodic, interconnected networks of monodisperse submicron pores extending over hundreds of micrometers. Depending on the technique of template removal, various phases of the inorganic oxide could be formed. For example, in the case of titania, an amorphous phase was formed upon extraction of TiO 2 and anatase by calcination at 450°C. The synthesis has also been expanded to other compositions including aluminophosphates and hybrid organosilicates, as well as silicates with bimodal distributions of meso-and macropores. The materials presented in this paper show the diversity of macroporous materials achievable with this technique. These structures could potentially find applications as chromatographic support materials, solid catalysts, battery materials, thermal insulators, or photonic crystals.

Colloidal crystal-templating methods have been used to prepare inverse opal photonic crystals of silica, mercaptopropyl-functionalized silica, titania, and zirconia. Ordered arrays of uniformly sized polymer spheres were infiltrated with fluid precursors capable of condensation or crystallization. After solidification of the material in the void spaces between the spheres, the polymer templates were removed by calcination or solvent extraction, leaving inverse replicas of the template arrays. By carefully controlling the synthetic procedures, gram-scale quantities of powdered macroporous materials exhibiting photonic crystal properties were obtained. For materials with crystalline walls (titania and zirconia), this required minimization of the size of the nanocrystalline grains. Because the periodicity introduced into the wall structure by the colloidal crystal templates was on the order of optical wavelengths, Bragg diffractions from the planes produced photonic stop bands in the visible spectra of these materials. The stop bands were manifested as brightly colored reflections and an optical filtering behavior of the materials. A crystallographic indexing of the optical spectrum of a polycrystalline inverse opal confirmed the fcc ordering of the pores. The optical properties of these materials were modified in predictable manners by numerous methods, including tailoring the pore size, filling the pores with fluids of various refractive indices, and changing the compositions of the solid material. The wavelengths of the colorful reflections (stop bands) were found to be proportional to the pore size and to vary linearly with the refractive index of the fluid filling the pores. The physical and synthetic modifications reported here allowed for the preparation of powders with optical reflections and bright colors spanning the entire visible spectrum.

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