Azo-Linkage Redox Metal-Organic Framework Incorporating Carbon Nanotubes for High-Performance Aqueous Energy Storage

The design of well-defined hierarchical free-standing electrodes for robust high-performance energy storage is challenging. We report herein that azo-linkage redox metal-organic frameworks (MOFs) incorporate single-walled carbon nanotubes (CNTs) as flexible electrodes. The in situ-guided growth, crystallinity and morphology of UiO-66-NO2 MOFs were finely controlled in the presence of CNTs. The MOFs' covalent anchoring to CNTs and solvothermal grafting anthraquinone (AQ) pendants endow the hybrid (denoted as CNT@UiO-66-AQ) with greatly improved conductivity, charge storage pathways and electrochemical dynamics. The flexible CNT@UiO-66-AQ displays a highest areal specific capacitance of 302.3 mF cm(-2) (at 1 mA cm(-2)) in -0.4 similar to 0.9 V potential window, together with 100% capacitance retention over 5000 cycles at 5 mA cm(-2). Its assembled symmetrical supercapacitor (SSC) achieves a maximum energy density of 0.037 mWh cm(-2) and a maximum power density of 10.4 mW cm(-2), outperforming many MOFs-hybrids-based SSCs in the literature. Our work may open a new avenue for preparing azo-coupled redox MOFs hybrids with carbaneous substrates for high-performance robust aqueous energy storage.

Automated summary

In this study, the researchers developed flexible electrodes by incorporating azo-linkage redox metal-organic frameworks (MOFs) with single-walled carbon nanotubes (CNTs). The resulting hybrid material, CNT@UiO-66-AQ, showed greatly improved conductivity, charge storage pathways, and electrochemical dynamics. It exhibited high capacitance and excellent cycling stability, outperforming other MOFs-hybrids-based supercapacitors reported in the literature. This work opens up new possibilities for the preparation of high-performance robust aqueous energy storage materials using azo-coupled redox MOFs hybrids with carbonaceous substrates.