Graphene‐Like Covalent Organic Framework with a Wide Band Gap Synthesized On Surface via Stepwise Reactions.

Developing graphene‐like two‐dimensional materials naturally possessing a band gap has sparked enormous interest. Thanks to the inherent wide band gap and high mobility in the 2D plane, covalent organic frameworks containing triazine rings (t‐COFs) hold great promise in this regard, whilst the synthesis of single‐layer t‐COFs remains highly challenging. Herein, we present the fabrication of a well‐defined graphene‐like t‐COF on Au(111). Instead of single/multiple‐step single‐type reactions commonly applied for on‐surface synthesis, distinct stepwise on‐surface reactions, including alkynyl cyclotrimerization, C−O bond cleavage, and C−H bond activation, are triggered on demand, leading to product evolution in a controlled step‐by‐step manner. Aside from the precise control in sophisticated on‐surface synthesis, this work proposes a single‐atomic‐layer organic semiconductor with a wide band gap of 3.41 eV. [ABSTRACT FROM AUTHOR]