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

Abstract

Novel Cu-VO_x and Fe-VO_x multiwalled nanotubes have been obtained by exchange of the protonated template in the parent dodecylamine-VO_x 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 VO_x layers occurs in the case of the Cu-VO_x nanotubes. The high structural flexibility of the VO_x nanotubes was evidenced at each step of this study. The controlled thermolysis of the Cu-containing VO_x nanotubes at 650 °C under N₂ leads to the formation of single-walled mesoporous V₂O₃ nanotubes and Cu⁰ nanoparticles.