Graphitic carbon nitrides are a research hotspot of two-dimensional (2D) materials, which attract more and more attention from researchers. Topological properties are a focus in graphitic carbon nitrides materials. Using first-principles calculations, we modified the g-C3N4 (formed by tri-s-triazine) by B atoms, proposing a novel two-dimensional monolayer, g-C6N7B, which showed excellent stability verified by positive phono modes, molecular dynamic simulations and mechanical criteria. The valence band and conduction band touch at the Γ point. Interestingly, g-C6N7B is topologically nontrivial, because the valance and conduction band can be gapped by the spin–orbit coupling (SOC) effect associated with robust gapless edge states. Additionally, molecular dynamic simulations indicate that g-C6N7B will still maintain good geometry structure when the temperature is as high as 1500 K. The flexibility of g-C6N7B is confirmed by its elastic constants and Young's moduli. This work opens an avenue for graphitic carbon nitride materials with topological properties.
