We developed a crystallization strategy that promotes in-plane growth of ZIF-L on nanoporous single-layer graphene, forming a few unit-cell-thick film. This 2D morphology of the MOF film allows us to achieve extremely attractive gas separation performance marked by H2 permeance over 1000 GPU accompanied with H2/N2 selectivities of over 40. While electron diffraction in TEM along the [001] zone axis seem to confirm the structure of ZIF-L, we could not obtain in-depth understanding of lattice parameter and crystallinity of the ZIF-L film, partly arising from the fact that ZIF-L is not stable under the electron beam. In particular, our interest is to understand the similarilty and differences of the novel 2d film with reference to the known 3D structure. Finally, the synthesis strategy, based on promotion of in-plane grain growth and etching of out-of-plane growth, is extremely attractive to replicate to wider range of two-dimensional MOFs and MOFs interesting for carbon capture.