▎ 摘　　要

Employing first-principles calculations, the structural, mechanical, and electro-optical properties of hydrogenated graphene/h-BN heterobilayer are explored systematically. Graphene/h-BN heterobilayer is a semimetal. Once hydrogenating the graphene/h-BN heterobilayer, it is transformed to a semiconducting diamane-like monolayer (C2BNH2). The C2BNH2 monolayer is predicted to have energetic, thermal, and dynamical stabilities and exhibits a moderate direct bandgap. The bandgap of C2BNH2 monolayer is variable with different atom bondings between graphene and h-BN layers. Also, the optical properties of the C2BNH2 are very sensitive to the atom bonding. Compared with the C-N bonding configuration, the C-B bonding configuration shows superior optical absorption for the visible and near-ultraviolet lights and owns a small binding energy of exciton. In addition, their in-plane elastic constants are comparable to that of graphene and ultimate tensile strengths under biaxial strain can be larger than 60 GPa. These features in the C2BNH2 monolayer endow it with great potential in electronic and optoelectronic devices.