Tailoring Electronic Properties of Precision Graphene Nanoribbons via Nanopore Engineering

The precise incorporation of nanopores into graphene nanoribbons (GNRs) offers a complementary strategy for modulating their opto-electronic properties beyond conventional width and edge engineering. However, a systematic understanding of the relationship between the structure and electronic properties of porous GNRs (pGNRs) remains experimentally unexplored due to the lack of rational synthetic strategies. Herein, we report two novel porous GNRs (pGNR 1 and pGNR 2) synthesized via solution-phase methods, featuring periodically arranged [18]annulene nanopores and gulf-edged architectures, along with a nonporous GNR (npGNR) as a counterpart. Utilizing efficient Diels-Alder polymerization and Scholl-type cyclization, these GNRs attain average lengths of up to 60 nm. The chemical identities of the synthesized GNRs were comprehensively characterized by IR, Raman, and solid-state NMR spectroscopy, complemented by theoretical calculations. To further elucidate the structural features underlying the observed properties, three representative model compounds (1, 2, and 3) corresponding to segments of the respective GNRs were synthesized and analyzed. UV-vis and THz spectroscopic analyses demonstrate that npGNR exhibits a relatively narrow optical bandgap of 1.63 eV and a high intrinsic charge carrier mobility of ∼40 cm² V^-1 s^-1, whereas pGNR 2 displays a wider bandgap of 1.91 eV with a reduced mobility of ∼27 cm² V^-1 s^-1. This study systematically elucidates the effects of nanopore incorporation on the electronic structure and charge transport properties of GNRs, offering a rational design framework for the design of nanopore-engineered carbon-based electronic materials.