▎ 摘　　要

We report a first-principles prediction of a new two-dimensional inorganic material, namely, the B2C graphene in which the boron and carbon atoms are packed into a mosaic of hexagons and rhombuses. In the B2C graphene, each carbon atom is bonded with four boron atoms, forming a planar-tetracoordinate carbon (ptC) moiety, a notion first conceived by Hoffmann et al. The B2C graphene is possibly a metal with a small overlap in the energy of conduction and valence bands. Like the carbon graphene and nanotubes, a B2C graphene sheet can be rolled into various forms of B2C nanotubes as well. Depending on the roll-up vector, the B2C nanotubes may become either a metal or a semiconductor. All B2C graphene nanoribbons are predicted to be uniformly metallic, regardless of their width and edge structure.