Surface-confined single-layer covalent organic framework on single-layer graphene grown on copper foil

The integration of 2D covalent organic frameworks (COFs) with atomic thickness with graphene will lead to intriguing two-dimensional materials. A surface-confined covalently bonded Schiff base network was prepared on single-layer graphene grown on copper foil and the dynamic reaction process was investigated with scanning tunneling microscopy. DFT simulations provide an understanding of the electronic structures and the interactions between the surface COF and graphene. Strong coupling between the surface COF and graphene was confirmed by the dispersive bands of the surface COF after interaction with graphene, and also by the experimental observation of tunneling condition dependent contrast of the surface COF. Co-condensation between benzene-1,3,5-tricarbaldehyde and p-phenylenediamine on a graphene surface leads to a surface covalent organic framework (COF) with single-layer thickness. Strong coupling between the surface COF and graphene was confirmed by the significant mixing of states and the relatively large interaction energy revealed by STM and DFT simulation.