Oxygen-assisted Cathodic Deposition of Copper-Carboxylate Metal–Organic Framework Films

Reductive deposition is an attractive strategy to prepare films of metal–organic frameworks (MOFs), but to cathodically deposit the intergrown dense films of MOFs containing readily reduced metal ions (e.g., Cu 2+ ) without the plating of the corresponding metals still remains a significant challenge. Here, we report the cathodic deposition of metallic copper-free films of two copper-carboxylate MOFs (HKUST-1 and MOF-14). Our strategy relies on the utilization of O 2 as probase to electrochemically trigger the crystallization of MOFs. Systematical cyclic voltammetry studies indicate that the favorable synergistic catalytic effects of the acidic copper ions and benzene-1,3,5-tricarboxylic acid ligands on the O 2 reduction can positively shift the deposition potential of HKUST-1 significantly to +0.05 V (vs Ag/AgCl), avoiding effectively the plating of metallic copper and facilitating greatly the control over the crystallization kinetics of MOFs. By the further optimization of experimental conditions relevant to reaction temperature, supporting electrolyte, O 2 concentration, and working potential, the intergrown dense MOF films with tunable thicknesses were deposited successfully on several commonly used electrodes including the highly oriented pyrolytic graphite, carbon fiber, carbon cloth, and fluorine-doped tin oxide.