On controlling the anodic electrochemical film deposition of HKUST-1 metal–organic frameworks

Anodic electrochemical synthesis presents itself as a powerful and rapid method to produce porous metal–organic framework (MOF) powders and deposit MOF films onto metal surfaces. Such layers are of interest for adsorptive, catalytic or sensor applications. However, electrochemical MOF synthesis is still in a preliminary stage while a need to better control the process and understand the influences of the process parameters emerges. This work focuses on controlling the deposition of copper-1,3,5-benzenetricarboxylate (HKUST-1, Cu-BTC) MOF layers and targeting different crystal sizes. Moreover, it aims to shed some light on the mechanisms underlying these changes. A number of strategies can be adopted to control the process and adjust the obtained crystal size. By adjusting the synthesis time or water content, the average crystal size can be controlled up to ∼10 μm for ethanol-based synthesis mixtures. The potential also has a pronounced effect, yet a suitable operation window must first be determined to avoid incomplete film formation or excessive film detachment. Furthermore, the influence of the solvent composition on the deposited film morphologies was investigated for mixtures of water, methanol, ethanol, 2-propanol, acetonitrile, N,N-dimethylformamide and dimethylsulfoxide.