Interfacial speciation controls the metal-framework partition during cathodic electrodeposition of Ni-MOF-74

Cathodic electrodeposition provides a versatile route to metal-organic framework (MOF) films, yet its application to frameworks built from infinite metal-oxide rods remains largely unexplored because framework assembly competes directly with metal electrodeposition. Here we report the cathodic electrodeposition of Ni-MOF-74 and identify the interfacial speciation that governs the partition of cathodic charge between metallic nickel deposition and framework growth. Cyclic voltammetry shows that coordination of Ni²⁺ by H₄DOBDC suppresses metallic nickel deposition by stabilising a carboxylate-coordinated pre-framework, while the electrolyte anion determines the extent to which cathodic charge is redirected towards MOF formation. Powder X-ray diffraction, infrared spectroscopy and density functional theory confirm the spontaneous formation of this intermediate prior to polarisation, supporting a stepwise pathway in which cathodically generated base completes framework assembly through phenolic deprotonation. We further demonstrate that dissolved oxygen provides a controllable electrochemical route to base generation capable of promoting the phenolic deprotonation required for MOF-74 assembly, offering improved control over the deposition process compared with conventional nitrate-based systems. Potentiostatic deposition reveals that the balance between framework growth and metal deposition can be tuned through the applied potential, enabling the formation of crystalline Ni-MOF-74-containing films while limiting, but not eliminating, nickel deposition. These findings establish interfacial speciation as the key factor controlling the metal-framework partition during cathodic MOF growth and provide mechanistic principles for electrochemical synthesis of MOFs based on infinite-rod secondary building units.