Immobilisation of Ni(II) and Zr(IV) metal-organic frameworks on electrodes using electrophoretic deposition

Metal-organic frameworks are materials which are constituted by an inorganic centre and organic ligand offering high crystallinity, high surface area and high permanent porosity. These structures show promising results in multiple applications due to their properties, especially their capacity for open-metal sites. The use of these structures for electrochemical applications, such as sensors and electrocatalysts, require their immobilisation on a conductive surface, as they are obtained in powder form using the most common method – solvothermal synthesis. Electrophoretic deposition, an indirect method, which focus on immobilising these materials in powder form postsynthesis on the surface of a conductive structure can be used for their immobilisation, that may offer several advantages in relation with other methods if further developed – those being simplicity and universality. This work focuses on the synthesis, immobilisation, and stability studies of these MOFs in the presence of water and in oxidative aqueous electrochemical medium. The obtained metal-organic framework powders and films were characterised using X-rays diffraction, Fourier Transform infrared spectroscopy and scanning-electron microscopy. The electrochemical studies were made using cyclic voltammetry. It was possible to form films of the MOFs UiO-66, UiO-66-NH2 and Ni-MOF-74 on the surface of fluoride-doped tin oxide glass using electrophoretic deposition, with all three MOF films showing stability in water and the UiO- 66 and UiO-66-NH2 films showing high stability as well in highly basic oxidative aqueous electrochemical medium.