In the present study, the photooxidation of gaseous trichloroethylene (TCE) was performed on Cr-Al-MCM-41 (predominantly a SiO2 framework) under visible light and UV light. This mesoporous Cr-containing MCM-41 material is a promising photocatalyst and exhibits excellent photoactivity. Moreover, the products of photooxidation under visible light are similar to those under UV-Iight illumination. The photocatalysis process occurs on isolated Cr6+ ions supported on a predominantly SiO2 framework. A possible mechanism leading to the photooxidation of TCE together with the detection of intermediates by gas chromatography-mass spectrometry is reported here. (C) 2004 Published by Elsevier Inc.