Preparation of organic mesoporous gel by supercritical/freeze drying

Resorcinol-formaldehyde (RF) aerogels were synthesized by sol-gel polyconde nsation of resorcinol with formaldehyde in a slightly basic aqueous solutio n and supercritical drying with carbon dioxide. The control of mesoporous s tructure 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 adsorp tion, 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 mesopor ous materials with high surface areas > 500 m(2)/g and large mesopore volum es > 0.8 cm(3)/g. Although the surface areas and mesopore volumes of RF cry ogels were smaller than those of RF aerogels, the cryogels were useful prec ursors of mesoporous carbons.