On-surface synthesis of porous nitrogen-doped graphene nanoribbons: Role of substrate orientation

Contributing to the design of functional graphene nanoribbons (GNRs) structures, we have synthesized porous and doped armchair graphene nanoribbons (N-GNRs) on Cu(111), Ag(100), and Ag(110) with atomic precision. The structural characterization and reaction step have been investigated using scanning tunneling microscopy. Despite pronounced differences in surface symmetry and chemical reactivity, the hierarchical polymerization of 2,7,11,16-tetrabromotetrabenzo[a,c,h,j]phenazine (TBTBP) through the on-surface Ullmann coupling consistently yields porous nitrogen-doped graphene nanoribbons with identical backbone structure, periodic pore architecture, and site-specific nitrogen doping. While ribbon length and growth kinetics vary across substrates—being limited on Cu(111), intermediate on Ag(100), and extended on Ag(110)—the intermolecular spacing and armchair edge topology remain preserved. These results demonstrate that the intrinsic molecular design of TBTBP dominates over substrate symmetry in defining the final nanoribbon structure. The substrate tolerance and structural fidelity observed here highlight the potential of this precursor platform for the synthesis of atomically precise porous GNRs on diverse supports, providing a promising route toward their integration on technologically relevant substrates.