Trinuclear Fe (III) acetato complex intercalated montmorillonite Fenton catalysts with large surface areas were prepared by a facile ion exchange process. The obtained samples were characterized by FT-IR, TGA-DSC, N-2-sorption and XPS in detail. To understand the microstructure of the active iron species in the montmorillonite, the Fe K-edge X-ray absorption spectra (XAFS) technique was also employed. The results showed that the trinuclear iron cluster was successfully intercalated into the layers of montmorillonite and the structure of the active iron species was an amorphous FeO(OH)-like structure after 500 degrees C post-treatment. When the prepared catalysts were used for the photo-Fenton reaction at room temperature, excellent activities were observed for degradation of phenol. Moreover, their activities were much higher than those of the traditional iron hydroxyl compound intercalated montmoillonite Fenton catalyst. The stable intercalated structure and the low leaching Fe concentration induced that the obtained catalyst can be operated for a long time. Meanwhile, the consumption of H2O2 and the change of pH in solution were also investigated in detail. (C) 2011 Elsevier B.V. All rights reserved.