Graphene nanoribbons (GNRs) are strips of graphene. Their electronic and magnetic properties can be tuned by changing their width and the structure of their edges. They can, for example, be synthesized by breaking apart graphene or carbon nanotubes. However, these methods do not allow for precise control over the resulting structures. “Bottom-up” synthesis strategies that use surface-mediated chemical reactions can be more precise, but are difficult to scale up.

Takashi Uemura, The University of Tokyo, Japan, and Japan Science and Technology Agency (JST), Kawaguchi, and colleagues have developed a method for GNR synthesis that is both precise and scalable. The team used a metal–organic framework (MOF) with nanochannels as a template to synthesize an armchair-type GNR with up to five carbon atoms in the cross-section (AGNR, pictured). They used the MOF [ZrO(biphenyl-4,4′-dicarboxylate)]_n to adsorb the AGNR precursor perylene inside its nanochannels. The precursor was then polymerized by heating to 400 °C. Finally, the MOF was removed using an aqueous solution of sodium ethylenediaminetetraacetate (EDTA), followed by treatment with dilute hydrofluoric acid.

The team obtained the desired AGNR in a yield of 28 %. When dibromoperylene was used as an alternative substrate, the polymerization temperature could be lowered to 300 °C and a yield of 54 % was achieved. The method allows the large-scale synthesis of nonsubstituted GNRs with precise control.

• Scalable and Precise Synthesis of Armchair-Edge Graphene Nanoribbon in Metal–Organic Framework,
  Takashi Kitao, Michael W. A. MacLean, Kazuki Nakata, Masayoshi Takayanagi, Masataka Nagaoka, Takashi Uemura,
  J. Am. Chem. Soc. 2020.
  https://doi.org/10.1021/jacs.0c00467