Polyoxometalate Steric Hindrance Driven Chirality-Selective Separation of Subnanometer Carbon Nanotubes

Subnanometer single-chirality single-walled carbon nanotubes (SWCNTs) are of particular interest in multiple applications.Inspired by the interdisciplinary joint of redox active polyoxometalates and SWCNTs, here we report a cluster steric hindrance strategy by assembling polyoxometalates on out surface of subnanometer SWCNTs via electron transfer and demonstrate the selective separation of monochiral (6,5) SWCNTs with a diameter of 0.75 nm by a commercially available conjugated polymer. Combined use of DFT calculations, TEM, and XPS unveil the mechanism that selective separation is associated with tube diameter-dependent interaction between tube and clusters. Sonication drives preferential detachment of polyoxometalate clusters from small-diameter (6,5) SWCNTs attributable to weak tube-cluster interaction, which enables polymer wrapping and separation of such released SWCNTs, while strong binding clusters with large-diameter SWCNTs act

as steric hindrance and block the polymer wrapping. The polyoxometalate-assisted modulation, which can be rationally customized, provides a universal and robust pathway for separation of SWCNTs.