Toward Metal-Organic-Framework-Based Supercapacitors: Room-Temperature Synthesis of Electrically Conducting MOF-Based Nanocomposites Decorated with Redox-Active Manganese

Nanocrystals of a zirconium-based metal-organic framework (Zr-MOF) were grown on carboxylate-functionalized carbon nanotubes (CNT) at room temperature to synthesize electrically conducting Zr-MOF-CNT nanocomposites. To further enable charge transport within the Zr-MOF phase via redox hopping under electrochemical conditions, redox-active manganese sites were then installed in the Zr-MOF and nanocomposites at room temperature by means of the solvothermal deposition in MOFs (SIM) technique. The redox hopping behavior of the Mn-decorated Zr-MOF nanocrystals was investigated. With the high electrical conductivity provided by the one-dimensional CNT bridges interconnecting multiple MOF nanocrystals, as well as the high-density accessible redox-active Mn sites supported by the Zr-MOF, the Mn-decorated Zr-MOF-CNT nanocomposites show more electrochemically addressable manganese sites and thus much higher pseudocapacitive performance compared to those of both the Mn-decorated Zr-MOF and the Mn-decorated CNT.