Topotactic redox reactions of copper(ii) and iron(iii) salts within VOx nanotubes

Abstract

Novel Cu-VOx and Fe-VOx multiwalled nanotubes have been obtained by exchange of the protonated template in the parent dodecylamine-VOx nanotubes with Cu(II) or Fe(III) salts. The intercalation of the transition metal species within the multiwalled structure of the tubes does not significantly affect the overall tubular morphology, but leads to a significant reduction of the inter-layer distance in the multiwalls from 3.02 to 1.09–1.05 nm. Electron microscopies, XRD, FTIR and XPS were used to study the nature of the host–guest interactions before and after the intercalation of the transition metal species. For the first time, it was observed that the substitution of dodecylamine by the transition metal salts induces a partial speciation of the intercalated species to their lower oxidation states, while an overall change in the structure of the VOx layers occurs in the case of the Cu-VOx nanotubes. The high structural flexibility of the VOx nanotubes was evidenced at each step of this study. The controlled thermolysis of the Cu-containing VOx nanotubes at 650 °C under N2 leads to the formation of single-walled mesoporous V2O3 nanotubes and Cu0 nanoparticles.