A novel method for tailoring porous structures of nanoporous materials using supercritical solvents

Abstract

Supercritical fluids (SCFs) were used for tailoring the structures of micro- and mesoporous silica with uniform pore sizes, C_nFSM-16 (n = 8, 10, 12 and 16), where the value n denotes the carbon atom number in the alkyl chain of the template surfactant. Silica precursors, tetraethylorthosilicate (TEOS) dissolved in supercritical CO₂ or in liquid ethanol, were impregnated onto FSM-16. The pore size of all the FSM-16 series decreased after coating in the supercritical solvent. On the other hand, silica was not introduced into pores smaller than that of the C₁₂FSM-16 by coating in the liquid solvent. This is elucidated in terms of the penetration difference into the nanoporous structures of supercritical solvents and liquid solvents. These results are compared with those of activated carbon with various pore sizes coated in supercritical solvents or in liquid solvents.