Diameter Controllable Separation of Single‐Walled Carbon Nanotubes by Simply Changing the Metal in Phenanthroline‐Based Supramolecular Polymers

Carbon nanotubes (CNTs) possess unique electronic and optical properties that are highly dependent on their structures. Therefore, diameter-selective synthesis and separation are meaningful for a wide range of their applications. Although various methods have been developed for CNT separations, challenges still remain in more efficient discrimination for diameters and removal of dispersants. Here, we present a novel approach for size-tunable diameter separation of single-walled carbon nanotubes (SWNTs) using metal-coordinating supramolecular polymers (M-PNB) consisting of phenanthroline-based nanobrackets (PNB) and metal ions (M). The helical wrapping of SWNTs with M-PNB is confirmed by transmission electron microscopy (TEM) analysis. Interestingly, Pd(II) and Co(II) ions with PNB show the large difference in diameter preference to the smaller (0.90 - 0.92 nm) and the larger (0.97 - 1.10 nm) diameters, respectively. Moreover, the combination of these two metal ions in M-PNB is found to enhance the selectivity to the specific (n,m)-SWNTs. This method offers not only size-tunable diameter selectivity but also significant improvements in extraction efficiency and the facile and thorough removal of the host molecules as compared to previous techniques.