Fig. 1

Schematic diagram of M1M2N6 located in the interior (-I), armchair-edge (− A1 ~ A6), and zigzag-edge (− Z1 ~ Z4) of graphene. The pink, green, blue, yellow, and balls denote H, C, N, M1, and M2 atoms, respectively.

Schematic diagram of M1M2N6 located in the interior (-I), armchair-edge (− A1 ~ A6), and zigzag-edge (− Z1 ~ Z4) of graphene. The pink, green, blue, yellow, and balls denote H, C, N, M1, and M2 atoms, respectively.