A new photocatalyst K2Sr1.5Ta3O10 with the 2D-layered perovskite crystal structure was prepared by the solid-state method. The UV-vis absorption spectra and the photoluminescence (PL) spectra of the anhydrous and hydrous K2Sr1.5Ta3O10 showed little difference, although the crystal structure changed from the orthorhombic to the tetragonal symmetry due to the water intercalation into the interlayer space. K2Sr1.5Ta3O10 exhibited photocatalytic activities for pure water splitting even without the assistance of cocatalysts. (c) 2007 Elsevier B.V. All rights reserved.