Periodic Mesoporous Silica Gels

We have synthesized monolithic particulate gels of periodic mesoporous silica by adding tetramethoxysilane to a homogeneous alkaline micellar precursor solution. The gels exhibit 5 characteristic length scales over 4 orders of magnitude: fractal domains larger than the particle size (>500 nm), particles that are ˜150 to 500 nm in diameter, interparticle pores that are on the order of the particle size, a feature in the gas adsorption measurements that indicates pores ˜10–50 nm, and periodic hexagonal arrays of ˜3 nm channels within each particle. The wet gel monoliths exhibit calculated densities as low as ˜0.02 g/cc; the dried and calcined gels have bulk densities that range from ˜0.3–0.5 g/cc. The materials possess large interparticle (˜1.0–2.3 cc/g) and intraparticle (˜0.6 cc/g) porosities.