N/Zr atomic ratio in the UiO-66-NH2 framework serves as an indicator of the linker vacancy defect density because N originates from the ligand. A defect-free crystal should have a ratio of 1. This ratio, quantified based on XPS (Supplementary note 2), was consistently ~0.58 in the non-vdW 2D UiO-66-NH2 films prepared using growth times from 5 to 30 minutes, suggesting a linker vacancy defect density of ~42% (Figure ). The linker defect is attributed to the use of acetic acid as a modulator which competes with the linker to coordinate with the zirconium-oxo cluster. This defect density in this study agrees well with literature data of 30-45% for UiO-66 synthesized in the presence of a modulator. The presence of a linker defect is not expected to alter the crystal structure because of an overall high coordination number. The thickness of the UiO-66-NH2 films could be controlled by varying the synthesis time from 5 to 30 minutes. Uniform contrast in SEM images indicated continuous and uniform film (Figure ). AFM analysis revealed that films synthesized in 5, 20, and 30 minutes had thicknesses of 1.7±0.2 nm (Figure and e), 3.8±0.4 nm (Figure and), and 4.7±0.4 nm, respectively (Figure and). These thicknesses correspond to 0.5, 1.5, and 2 unit cells of UiO-66-NH2 along the a-out-of-plane direction (Figure and S10, Supplementary note 3). 0.5 unit cell results from bisecting the face-centered cubic unit cell of UiO-66-NH2 as illustrated in Figure . We hypothesize that the film terminates at the metal node mainly because this will enable a strong cation-π interaction between the cationic hexanuclear Zr cluster and the π system in the crystalline graphene lattice. The hypothesis is supported by the high density of linker vacancy defect. For example, if one removes linkers on the top and bottom faces of a 0.5-unit-cell-thick film, it would result in ~33% defect density consistent with the high defect density in experimental data.