Evidence for ordering of cobalt ions in the microporous solid acid catalyst CoDAF-4 by single crystal X-ray diffraction and resonant X-ray powder diffraction

Abstract

Resonant (anomalous) powder X-ray diffraction has been successfully used to determine the site preferences of cobalt ions in the de-templated form of the microporous solid acid catalyst CoDAF-4, at low loadings of cobalt ions. These results are in accordance with conventional single crystal diffraction studies on the as synthesised material but at much higher concentrations of cobalt. It is shown that the cobalt ions preferentially occupy sites having the lowest configuration sequences thus minimising the number of potential Co–O–P–O–Co linkages.