▎ 摘　　要

The zero band gap of pristine graphene hinders its application in high-performance field effect transistors (FETs) at room temperature. The symmetry breaking of the sub-lattice, originated from the influence of substrates such as silicon carbide, hexagonal boron nitride as well as graphitic carbon nitride (C3N4), can produce a band gap in graphene. Herein, another novel kind of substrate, C2N, is employed to break the symmetry of the graphene sub-lattice, resulting in a band gap of about 0.40 eV in graphene. In combination with C2N through the weak van der Waals (vdW) interaction, graphene keeps its structural integrity and charge mobility. A band opening as large as 0.72 eV could be achieved through reducing the layer spacing to 3.2 angstrom. This is because the amount of electron transfer from graphene to C2N and the interaction between C2N and graphene increase with the decreasing interlayer spacing. Moreover, though the band gap of C2N is slightly altered, its electronic properties especially the direct band gap in visible region and the band dispersions are almost preserved. Thus, our theoretical results predict the promising multifunctional applications of C2N/graphene (C2N/G) heterostructures, including high-performance FETs and metal-free photocatalytic materials for water splitting.