MOF materials directly used as the electrode for energy storage are rarely reported. MOFs are crystalline sponge-like materials possessing large specific surface area (over 7,000 m² g^-1). Until now, more than 20,000 different MOFs have been synthesized within past decades. Unfortunately, the application of conventional MOFs in energy storage is largely hindered by their poor electrical conductivity.

Recently, Prof. XU Gang’s Group and Prof. WANG Yaobing’s Group from Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences (CAS), created a solid-state supercapacitor with electrodes made only from a highly conductive MOF nanowire arrays (Cu-CAT NWAs).

The MOF-based supercapacitor stored more energy per area (~22 μF cm⁻²) than most other carbon-based devices, and even comparable to those of graphene-based symmetric solid-state supercapacitors (18.9 – 25 μF cm⁻²). Notably, graphene precursor was synthesized under special care, strict conditions (e.g., strong oxidizing agents and strong acid) and long reaction time. In contrast, the reported conductive MOF material can be synthesis facilely in very mild conditions within a few hours.

Moreover, Compared to MOF powder electrode, this kind of nanostructured electrode can significantly reduce its intrinsic resistance and charge transfer resistance at the electrode/electrolyte interface, enabling effective charge/electron transport on the interface of nanowire arrays and electrolytes. The nanostructured electrode has 55% capacitance retention (more than 20% higher than the powder one).

The application of conductive MOF material in energy storage would be a significant breakthrough, and the results of this work will provide a great prospect for developing MOFs as an ideal class of electrode materials for supercapacitors. This work has been selected as inside back cover of Advanced Functional Materials.

This work was supported by the NSF of China (51402293, 21501173 and 21550110194), the Strategic Priority Research Program, CAS, (XDB20000000), Key Research Program of Frontier Science, CAS (QYZDB-SSW-SLH023) and NSF of Fujian Province (2016J06006, 2015J01230 and 2014J05027). We thank Prof. L.M. Zheng and Dr. S.S. Bao (Nanjing University, China) for their help with gas sorption measurements.

Left: This work was selected as the inside back cover of Advanced Functional Materials.

Right: Performance and structure of Cu-CAT NWAs based solid-state supercapacitor.