Tuning electrophoretic deposition parameters for the fabrication of MOF-based electrochemical coatings

The development of scalable, efficient methods for fabricating metal–organic framework thin films is vital for expanding their application in electrochemical sensing. In this work, we systematically explore the use of electrophoretic deposition to immobilise two zirconium-based metal-organic frameworks—UiO-66 and its amine-functionalised analogue UiO-66-NH 2 —onto fluorine-doped tin oxide (FTO) substrates. A comprehensive optimisation of solvent systems, deposition time, and electric field strength revealed that short deposition times (5 min) under an electric field of 90 V cm −1 in ethanol with 0.05 % acetic acid yield the most uniform, crystalline, and adherent coatings. This work presents, for the first time, the successful immobilisation of UiO-66-NH 2 using electrophoretic deposition. Structural integrity was confirmed via powder X-Ray diffraction and infrared spectroscopy, with scanning electron microscopy highlighting improved homogeneity in UiO-66-NH 2 coatings. Electrochemical characterisation in aqueous NH 4 Cl with variable NH 3 concentrations showed that UiO-66-NH 2 @FTO exhibited superior responsiveness compared to UiO-66@FTO and bare FTO. At an optimised potential of 1.1 V vs. Ag/AgCl, UiO-66-NH 2 @FTO demonstrated a clear, linear current response to both NH 4 + (0.475–0.495 M, R 2 = 0.9520, sensitivity = 8.044 mA M −1 ) and NH 3 (0.000–0.040 M, R 2 = 0.9521, sensitivity = 4.029 mA M −1 ). This enhancement is attributed to the amine functionalities that promote proton-coupled electron transfer (PCET) and increase analyte affinity. These findings highlight electrophoretic deposition as a viable strategy for metal-organic framework film fabrication and establish UiO-66-NH 2 @FTO as a promising platform for ammonia sensing. • UiO-66-NH 2 films were immobilised via electrophoretic deposition for the first time. • Optimised EPD yields uniform, adherent, and crystalline MOF coatings in 5 min. • Amine functionalisation enhances ammonia sensitivity via proton-coupled transfer. • UiO-66-NH 2 @FTO shows superior response to NH 4 + and NH 3 at 1.1 V vs. Ag/AgCl. • EPD offers a scalable route to MOF-based electrochemical sensing platforms.