The selective oxidation of saturated C-H bonds is a crucial step in many industrial processes. Recent we have discovered an alternative green one-step route for the selective oxidation of methane to methanol. The key to this significant scientific breakthrough is the apparent activation of methane and the oxidant (H2O2) by a suitable Lewis acid (Fe-containing zeolites). Several spectroscopic techniques have demonstrated that Fe is initially present as an isomorphously substituted framework atom. The operational catalyst requires heat treatment at temperatures up to 750 ºC, where a proportion of Fe sites becomes extra-framework species Understanding this process is a key requirement to optimise the catalytic properties and powder neutron diffraction studies can provide a detailed understanding o of the ordered distribution of substituted metal sites within zeolytic frameworks.