Metal-organic frameworks (MOFs) are highly desired to develop a synthetic chemistry yielding two-dimensional (2D) film with thickness of just a few unit-cells of structure. However, realization of 2D MOF films remains elusive to date. The progress in this direction has been limited to the synthesis of layered particles. We have recently developed a crystallization strategy that promotes in-plane growth of MOFs (2DZIF, UiO-66-NH2 and UTSA-280) on an epitaxial substrate forming a unit-cell-thick film. The thickness of the 2DMOF film can be adjusted by simply tuning the growth time under the synthetic conditions.