Effect of Double Ligands on the Structure and Electrochemical Performance of Metal–Organic Framework as the Electrode Material of High-Performance Supercapacitors

Metal–organic frameworks (MOFs) are attractive electrode materials for supercapacitors due to their high specific surface area, tunable pore structure, and excellent electrochemical properties. However, the factors that affect MOF morphology and performance still lack in-depth research. Herein, the impact of the mixture ligands of terephthalic acid (PTA) and 1,3,5-benzotricarboxylic acid (BTC) on the structure and electrochemical performances of MOFs was thoroughly explored. The micromorphology and crystalline structure of Ni-MOFs were modulated by adjusting the organic ligand ratio. And the optimized MOF structure facilitated electrolyte ion diffusion and then provided abundant redox active sites, which thereby significantly enhanced the electrochemical performance. In particular, Ni-MOFs with a molar ratio of PTA:BTC at 0.5:0.5 (NiMOF-0.5) exhibited superior electrochemical properties, with a specific capacity as high as 2009.12 F g–1 at a current density of 1 A g–1. Furthermore, an asymmetric supercapacitor (NiMOF-0.5//AC) was assembled with prepared NiMOF-0.5 as a cathode and biomass-based activated carbon as an anode, which exhibited a maximum energy density of 32.19 Wh kg–1 at a current density of 1 A g–1 with a power density of 970.49 W kg–1. After 4000 cycles, it still kept a 95.23% of capacity retention. The results demonstrated that the dual-ligand strategy provided a promising approach for preparing MOF-based electrode material of supercapacitors.