Insights into the host-guest systems of single-walled-carbon-nanotube-confined polyoxometalates

Polyoxometalates (POMs) have attracted burgeoning research interests for their rich redox activities, well-defined structures, and manipulatable chemical properties. Stemming from their fully oxidized state and high solubility, however, POMs usually confront two hurdles of electrical insulation and chemical/electrochemical instability. Confining POMs inside single-walled carbon nanotubes (SWNTs) represents an effective route to address these issues and trigger the emerging properties of guest molecules and host nanocontainers, as well as their synergistic interactions. This perspective aims to elucidate the prominent research status in this emergent field, including the redox-driven encapsulation of POM clusters inside SWNTs, the confinement effect of nanotubes on inner POMs, influences of encapsulated clusters on SWNT structures, and state-of-the-art applications of such a kind of host-guest systems in SWNT separation, electrochemical energy storage, electrocatalysis, and building blocks for functional materials. Finally, the challenges and prospects for future exploitation of one-dimensional POM@SWNT heterostructures are discussed, which are expected to encourage in-depth fundamental research and diverse applications.