On‐Surface Synthesis of Variable Bandgap Nanoporous Graphene

Abstract Tuning the bandgap of nanoporous graphene is desirable for applications such as the charge transport layer in organic‐hybrid devices. The holy grail in the field is the ability to synthesize 2D nanoporous graphene with variable pore sizes, and hence tunable band gaps. Herein, the on‐surface synthesis of nanoporous graphene with variable bandgaps is demonstrated. Two types of nanoporous graphene are synthesized via hierarchical CC coupling, and are verified by low‐temperature scanning tunneling microscopy and non‐contact atomic force microscopy. Nanoporous graphene‐1 is non‐planar, and nanoporous graphene‐2 is a single‐atom thick planar sheet. Scanning tunneling spectroscopy measurements reveal that nanoporous graphene‐2 has a bandgap of 3.8 eV, while nanoporous graphene‐1 has a larger bandgap of 5.0 eV. Corroborated by first‐principles calculations, it is proposed that the large bandgap opening is governed by the confinement of π‐electrons induced by pore generation and the non‐planar structure. The finding shows that by introducing nanopores or a twisted structure, semi metallic graphene is converted into semiconducting nanoporous graphene‐2 or insulating wide‐bandgap nanoporous graphene‐1.