A 0.1 M FeCl3 aqueous solution was hydrothermally treated in a 1.5-dm(3) stainless steel autoclave at varied temperatures (T-h: 110-200 degreesC). Highly ordered cubic particles with uniform micropores 0.8 nm in diameter are produced at T-h = 115 degreesC, although the cubic particles become less uniform with wide pore size distribution by raising the T-h. (C) 2003 Elsevier Inc. All rights reserved.