Metal-organic frameworks have been widely investigated for their promising gas adsorption properties; however, their syntheses often utilize harsh, toxic, and time consuming synthetic conditions relying on high temperatures and multi-day reactions. A number of improvements must be made to be able to utilize these materials in efficient large-scale applications. Recently, electrochemical methods have been explored for the synthesis of these porous materials. These have included reductive deprotonation of the organic linker and/or anodic dissolution of the metal source. Although these techniques have shown promise, the former is carried out at very negative potentials that can co-reduce metal ions in solution. The latter dissolves the electrode in solution to produce metal ions, significantly depleting the electrode during synthesis. The oxidation of the metal ion in solution offers a novel approach to overcome aforementioned flaws in electrochemical techniques. When both the organic linker and metal source, such as Fe2+, are placed in solution with a stoichiometric amount of base and an oxidative potential is applied, the metal source at the electrode will oxidize to the Fe3+ ions needed to form the framework. As an added benefit of this technique, uniform, thin layer film growth on the electrode surface is attainable. Here, the electrochemical oxidation of Fe2+ in the presence of lutidine and terephthalic acid affords MIL-101 in high yield, as confirmed by powder X-ray diffraction. SEM and XPS have been used to observe both the individual crystallite size and atom composition of the formed product; the results concur with those of the solvothermally synthesized MIL-101. Furthermore, gas adsorption data have proved that these electrochemical materials possess a surface area that rivals that of the solvothermally synthesized material.

Electrochemical synthesis of metal-organic frameworks on modified electrode surfaces

256th National Meeting (2018)

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