Tunable electron property induced by B-doping in g-C 3 N 4 .

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-C 3 N 4 (formed by tri- s -triazine) by B atoms, proposing a novel two-dimensional monolayer, g-C 6 N 7 B, 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-C 6 N 7 B 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-C 6 N 7 B will still maintain good geometry structure when the temperature is as high as 1500 K. The flexibility of g-C 6 N 7 B is confirmed by its elastic constants and Young's moduli. This work opens an avenue for graphitic carbon nitride materials with topological properties.