Zn2(bim)4 is a zinc-based monoclinic MOF composed of zinc as the metal node and benzimidazole (bim) as the linker (Fig. ) . The first hurdle in achieving the target of oriented, in-plane growth is homogeneous nucleation where a nucleus formed in the bulk solution can attach with random orientation onto the growing film disrupting the oriented growth. The second hurdle is the substrate where the roughness of the substrate can hamper the in-plane growth especially for the synthesis of unit-cell-thick films. These hurdles were overcome using an ultra-dilute growth precursor solution and atomic-smooth graphene as the substrate. The former delays homogenous nucleation whereas the latter provides the needed smoothness for the propagation of unit-cell-thick film. With this strategy, the direct synthesis of Zn2(bim)4 film could be achieved for the first time.