Polyoxometalates (POMs) have received considerable attention in recent years due to their rich redox properties and potential applications in energy storage.¹ Due to their discrete nature, the use of POMs as components in energy storage devices relies on their stable combination with conductive supports.² Carbon nanotubes (CNTs) are stable, hollow cylinders made entirely of carbon. These nanostructured carbons are highly conductive, mechanically strong and can be functionalized.³ By encapsulating molecular materials within CNTs, their properties can be enhanced.

This work describes the first report of the encapsulation of the Keggin [PW₁₂O₄₀]^3- and Wells-Dawson [P₂W₁₈O₆₂]^6- heteropolyanions within carbon nanotubes (CNTs), along with detailed structural, chemical and electronic characterization. Transmission Electron Microscopy (TEM) confirms the presence of encapsulated POMs, as well as providing the necessary energy to perform observable chemical transformations within the CNT. Access to POM redox properties from within the CNT upon encapsulation is described, and the POM electrochemistry is shown to be stabilized across a greater range of conditions and cycles than typically possible. Investigations using Raman spectroscopy probe the electronic coupling between the host and guest, showing electron transfer between the two.

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3. Miners, S. A.; Rance, G. A.; Khlobystov, A. N., Chemical reactions confined within carbon nanotubes. Chem. Soc. Rev. 2016, 45 (17), 4727-4746.