Single-walled carbon nanotubes (SWCNTs) are useful nanomaterials with a variety of possible applications, e.g., in materials science. Their properties are influenced by their diameter, so controlling this value is important in nanotube synthesis. There are methods for the templated synthesis of SWCNTs using organic templates, but the efficient preparation of SWCNTs with narrow diameter distributions is still challenging, and suitable templates can be difficult to obtain.

Yue Hu, Wenzhou University, China, Qing-Hui Guo, Zhejiang University, Hangzhou, China, and Tsinghua University, Beijing China, Feihe Huang, Zhejiang University, and colleagues have developed a method for the diameter-controlled synthesis of SWCNTs using [2n]collarenes (n = 6, 8, 10) as rigid organic templates. [2n]Collarenes are hydrocarbon belts consisting of alternating phenylene and 1,4-cyclohexadiene rings. The team first prepared pillar[n]arenes as precursors, which were composed of alternating phenylene and para-alkoxyphenylene units, linked via methylene bridges. The precursors were synthesized using Suzuki coupling reactions.

The precursors were then demethylated to give hydroxy-functionalized intermediates, which were converted to the corresponding triflates. A coupling with isopropenylboronic acid then gave isopropenyl-functionalized intermediates. The desired collarenes were obtained via intramolecular Friedel–Crafts alkylations in yields of 33–44 %.

The synthesized belt-shaped templates were loaded onto a quartz substrate and used for the growth of SWCNTs by chemical vapor deposition (CVD). The researchers found that the diameters of the resulting SWCNTs corresponded well to the diameters of the templates used. According to the team, the work represents the first use of hydrocarbon belts as templates in the growth of SWCNTs, and the rigid structure of the collarenes makes them well-suited to this task.

• Diameter-Controlled Synthesis of Carbon Nanotubes Using [2n]Collarenes as Rigid Organic Templates,
  Ting Liu, Linxi Zhu, Ke Liu, Zhe Liu, Yang Liu, Yifei Zhang, Yue Hu, Qing-Hui Guo, Feihe Huang,
  J. Am. Chem. Soc. 2024.
  https://doi.org/10.1021/jacs.4c08536