Stepwise On-Surface Synthesis of Porous Carbon Nanoribbons with Notched Zigzag Edges

Bottom-up synthesis of carbon nanomaterials embedded with periodic arrays of nanoporous structures is of great interest for potential applications in nanotechnology. In limited examples, lateral fusion of polymer chains or armchair/chevron graphene nanoribbons with phenyl functional groups upon dehydrogenative coupling has been observed for the generation of porous nanoribbons or nanoporous graphene. Here we report a stepwise on-surface synthesis of porous carbon nanoribbons upon hierarchical Ullmann coupling for promoting highly selective inter-ribbon connections, which results in porous carbon nanoribbon structures with a notched zigzag edge and variable widths. By combining scanning tunneling microscopy and atomic force microscopy, the nanoporous structure and the corresponding electronic structures are fully characterized, which shows that localized electronic states are generated at pore–ribbon interfaces and ribbon zigzag edges. Further first principle calculations unveil the observed electronic states near the Fermi level originating from the two flat bands upon nanoporous structure imprinting. Our results provide a promising strategy for the atomically precise synthesis of porous carbon nanoribbons with engineered electronic structures, which can potentially enrich the synthetic routes to porous nanostructures and also expand the variety of carbon nanomaterials with characteristic electronic properties.