The structure of the active iron site in Fe/ZSM-35 was investigated by in situ resonance Raman spectroscopy combined with Mossbauer spectroscopy and DFT calculations. In situ UV resonance Raman spectra coupled with Fe-57 Mossbauer spectra suggest that the active Fe site for N2O decomposition is an Fe-2(mu-O) site, characterized by a Raman band at 875 cm(-1). In situ visible resonance Raman spectra reveals the formation of an Fe-2(mu-O)(2) site with a feature Raman band at 730 cm(-1) upon N2O reacts with the Fe-2(mu-O) site. The Raman band intensity at 730 cm(-1) is decreasing after exposing the Fe-2(mu-O)(2) site to CH4 due to the formation of methoxide species which mimics the biocatalysis of soluble methane monooxygenase (sMMO). Crown Copyright (C) 2013 Published by Elsevier Inc. All rights reserved.