The optimal Zn 2+ and bim -concentrations were between 4.69 to 9.38 mM and 4.5 to 9 mM, respectively, corresponding to a metal/linker ratio ranging from 0.52 to 2.08 (Fig. and Supplementary Fig. ). Within this composition window, a uniform and continuous layer was formed on various graphitic substrates including highly-oriented pyrolytic graphite (HOPG) (Supplementary Fig. ), chemical vapor deposition (CVD) derived single-layer graphene resting on Cu foil (Supplementary Fig. ), and CVD graphene transferred on a Si/SiO2 wafer (Supplementary Fig. ). The Zn2(bim)4 film, prepared on HOPG with a reaction time of 10 minutes, was analyzed using optical and scanning electron microscopy (SEM, Fig. ). A distinct and uniform contrast could be observed between the film and the substrate (Supplementary Fig. ). The uniformity of the contrast suggests that the film is smooth, continuous, and macroscopically uniform. Further examination by atomic force microscopy (AFM) at the edge of the film revealed a thickness of ~4 nm (Fig. and). This thickness corresponds to two unit-cells of Zn2(bim)4 along the c-out-of-plane direction (Supplementary Fig. ).