Abstract
Pure silica of high surface area was prepared by the slow evaporation of colloidal solutions of silicic acid in organic solvents. The porous silica materials were characterized by nitrogen adsorption, adsorption of volatile organic molecules, and 29Si magic angle spinning (MAS) NMR. The absorption properties and the high concentration of silanols, detected by 29Si NMR resonances, are consistent with a surface area of 600−700 m2/g. The high surface area and the virtual lack of long-range order suggest the model of a “sponge” containing open and interconnected pores. The size of the pores or channels is relatively homogeneous and is affected quite markedly by the organic preparation medium. The pores of the structure obtained using tetrahydrofurane are on the subnanometer scale, an indication that the diffusive phenomena must be influenced by intimate organic−inorganic interactions during the slow evaporation of the solvent.
Published Version
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