Cu-exchanged Hydroxyapatites: understanding the ionic exchange mechanism and potential towards selective redox catalysis by in situ XAS

Hydroxyapatites (HA) are versatile materials that can substitute any of their basic units by ionic species possessing similar characteristics while maintaining their structural entity. Commonly, a cationic exchange at a superficial level is performed by substituting the Ca2+ by a similar metal cation (M2+). The substitution of the Ca2+ by Cu2+ ions is particularly interesting, due to the versatility of Cu in many different applicative fields, including heterogeneous catalysis. Yet, the knowledge of the nature of the Cu substituents at a molecular level is still scarce. Driven by encouraging findings about the red-ox activity of Cu-HA, we propose to study by in situ XAS a batch of Cu-HA with a Cu loading of 2-7 wt. % and high surface area. The proposed study will provide a full characterization of Cu-HA in terms of Cu oxidation state and coordination environment, under model conditions designed to explore the potential of these materials towards selective oxidation catalysis.