The chemical compositions of the deposited films were analyzed through X-ray photoelectron spectroscopy (XPS). The binding energy (BE) for Zr 3d5/2 and Zr 3d3/2 were centered at 183.2 eV and 185.6 eV, respectively, with a peak splitting of 2.4 eV (Figure , S5a). Two N 1s peaks at 399.6 eV and 401.3 eV were observed (Figure , S5b), corresponding to the primary amine in BDC-NH2 and the ammonium ion formed from the reaction between primary amine and H2O, respectively. These BE are consistent with the literatures on UiO-66-NH2, indicating that the chemical environments of Zr and N within the nanometer-thick films were similar to that in the bulk crystal (Supplementary note 1, Figure ). The XPS data, collected from three separate regions on the thin film, were consistent indicating that the film was homogeneous in composition (Figure ). As expected, Zr and N were not present in the HOPG substrate (Figure ).