In a Petri dish containing 18 ml of Zn2(NO3)2 aqueous solution at room temperature, various substrates -HOPG, CVD graphene on Cu foil, and graphene/Si/SiO2 -were partially immersed. Subsequently, 2 ml of an aqueous solution of bim was added. After a predetermined duration, the substrates were carefully removed to stop the reaction. This procedure allowed us to distinguish the edge between the bare substrate and the Zn2(bim)4 film, facilitating the observation of thickness and contrast using SEM and AFM. Further details on how the concentration of the precursor solution and the reaction time influence the outcomes are discussed in Supplementary Note 1.