A Hybrid Supercapacitor based on Porous Carbon and the Metal-Organic Framework MIL-100(Fe)

Composite supercapacitor electrodes based on carbon nanotubes, carbon black, and a metal-organic framework with iron-(III) coordination centers [MIL-100(Fe), MIL-88B(Fe), or MIL-53(Fe)] were prepared and tested with several aqueous electrolytes. A correlation between hydrated ion size and the electric response of the electrodes was found, which sheds light on how these materials work as energy-storage devices. MIL-100(Fe) shows the most promising results, and the capacitance obtained with the samples in the solutions used is higher than that of a mixture of carbon and nanotubes in the same solution. Unfortunately, shortcomings due to reductive dissolution still hamper the long-term cyclability of the electrodes.