A microporous clay mineral with organic-inorganic hybrid pillars was synthesized using a hydrochloric acid (HCI)/ethanol extraction method after intercalation of tetraethoxysilane (TEOS) or TEOS/methyltriethoxysilane (MTS) into the cetyltrimetylammonium ion (CTA)-exchanged vermiculite. The products retained their layered structure, due to the formation of stable pillars by the polymerization of hydrolyzed TEOS and MTS during the HCI/ethanol treatment. The BET surface areas, which increased to above 500 m(2) g(-1) with an increase in the HCI concentration up to 0.4 mol dm(-3), are nearly equal to that of the calcined product obtained by the conventional method. However, the pore sizes of HCI/ethanol-treated materials were narrower than those of the calcined product, owing to the formation of the polysiloxane networks in the gallery. A water adsorption study showed that the product treated with a TEOS/MTS mixture had a hydrophobic surface as a result of the successful incorporation of methyl groups at the surface of the pillars. This novel method is advantageous for the synthesis of organophilic pillared clays with different kinds of organic materials in the interlayers. (C) 2003 Elsevier Inc. All rights reserved.