Microwave-assisted synthesis of pillared Ni-based metal–organic framework and its derived hierarchical NiO nanoparticles for supercapacitors

Metal–organic frameworks have emerged as promising precursors and templates for constructing various electrode materials. However, most of MOFs are usually synthesized by time-consuming solvothermal method, which reduces the efficiency of MOFs engaged strategy of fabricating nanostructured electrode materials. In this work, a pillared Ni-MOF (Ni(bdc)(ted)_0.5) has been successfully prepared by a facile microwave-assisted method in 30 min. Hierarchical NiO nanoparticles are obtained after annealing the Ni-MOF at various temperatures. When acting as electrode material for supercapacitor, the NiO-350 delivers higher specific capacitance (248.28 F g⁻¹ at 0.5 A g⁻¹), rate capacitance (61.7% at 10 A g⁻¹) and cycling stability (74.3% over 2000 cycles) than those of Ni-400 and Ni-450. The large surface area can provide substantial electroactive sites, and the hierarchical porous structure is beneficial for transport of ions and more electrolyte ions can penetrate into the inner of surface of electrode material. Besides, the nanosized NiO can increase the conductivity of the electrode. All these factors contribute to the superior electrochemical performance of Ni-350. Since microwave-assisted synthesis of MOFs is rapid and facile, more nanostructured electrode materials, such as carbons and metal sulfides can be synthesized by this method followed by appropriate treatment.