Structural characterisation of copper-containing manganese oxide octahedral molecular sieve (Cu-OMS-2) materials by X-ray absorption spectroscopy and cyclic voltammetry

X-ray absorption spectroscopy (X-ray absorption near-edge structure including pre-edge features and extended X-ray absorption fine structure studies) and cyclic voltammetry analyses were used to study copper substituted manganese oxide octahedral molecular sieve (Cu-OMS) microporous materials. The results from the XAS study have been interpreted in terms of possible locations of Cu2+ ions in the microporous zeotypic OMS-2 structure. According to the synthetic route, the Cu2+ ions are expected to interact with the surface atoms, and do not replace any of the framework atoms. The results are consistent with copper interacting with lattice oxygen and manganese atoms, and are therefore also consistent with copper being sited within the channels of OMS-2. Qualitative pre-edge studies on manganese in copper doped OMS-2 show octahedral Mn4+. The latter confirmed by cyclic voltammetric analyses giving similar voltammograms as for the manganese dioxide and non-mobility for Mn2+ in the OMS-2 material.