Preparation of organic mesoporous gel by supercritical/freeze drying

Resorcinol-formaldehyde (RF) aerogels were synthesized by sol-gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution and supercritical drying with carbon dioxide. The control of mesoporous structure of the aerogels was studied by changing the amounts of resorcinol, formaldehyde, distilled water, and sodium carbonate (basic catalyst) used in the polycondensation. As a result of characterization by nitrogen adsorption, the mesopore radius of the RF aerogel was controlled in the range of 2.5 - 9.2 nm. After the hydrogels were immersed in excess of t-butanol, RF cryogels were prepared by freeze drying. The cryogels prepared were mesoporous materials with high surface areas > 500 m(2)/g and large mesopore volumes > 0.8 cm(3)/g. Although the surface areas and mesopore volumes of RF cryogels were smaller than those of RF aerogels, the cryogels were useful precursors of mesoporous carbons.