Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500 degrees C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35 degrees to 80 degrees C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140 degrees C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.

A family of highly ordered mesoporous (20−300 Å) silica structures have been synthesized by the use of commercially available nonionic alkyl poly(ethylene oxide) (PEO) oligomeric surfactants and poly(alkylene oxide) block copolymers in acid media. Periodic arrangements of mescoscopically ordered pores with cubic Im3̄m, cubic Pm3̄m (or others), 3-d hexagonal (P63/mmc), 2-d hexagonal (p6mm), and lamellar (Lα) symmetries have been prepared. Under acidic conditions at room temperature, the nonionic oligomeric surfactants frequently form cubic or 3-d hexagonal mesoporous silica structures, while the nonionic triblock copolymers tend to form hexagonal (p6mm) mesoporous silica structures. A cubic mesoporous silica structure (SBA-11) with Pm3̄m diffraction symmetry has been synthesized in the presence of C16H33(OCH2CH2)10OH (C16EO10) surfactant species, while a 3-d hexagonal (P63/mmc) mesoporous silica structure (SBA-12) results when C18EO10 is used. Surfactants with short EO segments tend to form lamellar mesostructured silica at room temperature. Hexagonal mesoporous silica structures with d(100) spacings of 64−77 Å can be synthesized at 100 °C by using oligomeric nonionic surfactants. Highly ordered hexagonal mesoporous silica structures (SBA-15) with unusually large d(100) spacings of 104−320 Å have been synthesized in the presence of triblock poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) copolymers. SBA-15 mesoporous structures have been prepared with BET surface areas of 690−1040 m2/g, pore sizes of 46−300 Å, silica wall thicknesses of 31−64 Å, and pore volumes as large as 2.5 cm3/g. A novel cubic (Im3̄m) cage-structured mesoporous silica structure (SBA-16) with a large cell parameter (a = 176 Å) has been synthesized using triblock copolymers with large PEO segments. The EO/PO ratio of the copolymers can be used to control the formation of the silica mesophase:  lowering this ratio of the triblock copolymer moieties promotes the formation of lamellar mesostructured silica, while higher ratios favor cubic mesostructured silica. Cubic mesoporous structures are also obtained when star diblock copolymers are used as structure-directing agents. The calcined ordered mesoporous silicas reported in this paper are thermally stable in boiling water for at least 48 h. The assembly of the inorganic and organic periodic composite materials appears to take place by a hydrogen bonding (S0 H+)(X-I+) pathway. The assembly rate r increases with increasing concentration of [H+] and [Cl-], according to the kinetic expression r = k[H+]0.31[Cl-]0.31.

The formation of continuous mesoporous silica films with large periodic cage and pore structures is reported here. The authors use low‐cost commercially available triblock copolymers and poly(ethylene oxide) non‐ionic surfactants as the structure‐directing agents in conjunction with dip‐coat processing. In the Figure a transmission electron microscope image of a calcined hexagonal mesoporous silica film is shown.

The diameters of primary mesopores in materials with well-defined cylindrical pores can be accurately determined by the 4V/A method when the volume and surface area are determined by a standard adsorption method and 13.5 Å2 is used as the molecular area of adsorbed nitrogen. A simple method for determining standard adsorption using the statistical thickness of the adsorbed gas layer defined by Frenkel−Halsey−Hill (FHH) theory is described. For materials in which the pores are not cylindrical or well-defined, a simplified Broekhoff−de Boer method can be used to determine pore dimensions. The use of Hill's approximation for the thickness of the adsorbed gas layer in the Broekhoff−de Boer method simplifies its use. The results of these methods on small pore MCM-41 materials, large pore SBA-15 materials, and spherical pore mesocellular foams are reported.

Large, hard, transparent, mesoporous silica spheres are synthesized in one step by using oil-in-water emulsion chemistry under basic conditions with cationic surfactants and (n-BuO)₄Si. The pores are shown by TEM and nitrogen absorption studies to be monodispersed in size, with total surface area over 1000 m²/g