Biomimetic oxidation with Fe-ZSM-5 and H2O2? Identification of an active, extra-framework binuclear core and an FeIII-OOH intermediate with resonance-enhanced Raman spectroscopy

Developing inorganic materials that can mimic nature's ability to selectively oxidise inert C-H bonds remains a topic of intense scientific research. In recent years, zeolitic materials containing Fe and/or Cu have been shown to be highly active, heterogeneous catalysts for the selective oxidation of alkanes (including methane), amongst a range of other related oxidation challenges. By using resonance-enhanced Raman spectroscopy, we demonstrate that, following high-temperature pre-treatment (activation), Fe-containing ZSM-5 possesses an active binuclear core, and forms a key Fe-OOH intermediate upon activation with H<inf>2</inf>O<inf>2</inf>. Both factors are reminiscent of biological oxidation catalysts, and may account for the unique ability of this material to selectively oxidise methane to methanol at low temperature. A pre-ferryl cat: Through insitu resonance-enhanced Raman spectroscopy, we identify an active, binuclear Fe-O(H)-Fe core and an Fe^III-OOH intermediate in Fe-containing ZSM-5 following activation with H<inf>2</inf>O<inf>2</inf>. The pre-ferryl nature of this biomimetic intermediate may account for the unique ability of this solid catalyst to selectively oxidise methane to methanol under mild conditions.