In the case of molecular graphene, carbon monoxide molecules on Cu(111) surface can be used. Other materials have been shown to be suitable for making molecular graphene suchlike Coronene. Substrates such as Cu(111) are interesting because they have a 2D free-electron-like surface state. If CO molecules are placed onto appropriate positions, as the Cu(111) surface state is scattered from the CO molecules, the surface state electron gas can be confined onto different geometries (e.g. a honeycomb).