Weak base-modulated synthesis of bundle-like carbon superstructures from metal-organic framework for high-performance supercapacitors

In this work, we demonstrate the combination of “weak base-assisted hydrolysis” strategy with high-temperature carbonization to transform Zn-MOF-74 to porous bundle-like carbon superstructures. The utilization of weakly basic bicarbonates, such as NaHCO3, KHCO3, and NH4HCO3, is found to promote the formation of bundle-like superstructures composed of a mixture of zinc carbonate hydroxide/zinc hydroxide /Zn-MOF-74 derivative (labeled as ZNH-130), while the use of a strong base (NaOH) favors the generation of flower-like ZnO particles. Benefiting from the ultrahigh surface area (>1,200 m2 g−1) and the good interconnection of the assembling nanorods, the optimum bundle-like carbon superstructures (labeled as SBC-850) show a high specific capacitance of 270 F g−1 in 1.0 M H2SO4 at a current density of 1 A g−1. Furthermore, the SBC-850 sample can retain over 99% of its initial capacitance after 10,000 cycles at a high current density of 20 A g−1 due to the high structural and compositional stability of the bundle-like superstructures based on post-cycling XRD and SEM observations. The symmetric supercapacitor assembled using SBC-850 as the positive and negative electrodes exhibits a maximum energy density of 25.8 Wh kg−1 at a power density of 2400 W kg−1. These results highlight the promising potential of porous carbon superstructures for supercapacitor applications.