A drive towards a bi-linker strategy: tailoring MOF efficiency for advanced battery-supercapacitor hybrid devices

Metal-organic frameworks (MOFs) have emerged as promising materials for supercapacitor applications; however, challenges such as limited conductivity, stability, and rate capability hinder their practical implementation. Despite extensive efforts, including hybridization and bimetallic strategies, a significant performance gap remains. In this work, we introduce a drive towards a bi-linker approach to engineer nickel-based MOFs, systematically varying the ratio of pyridine-2,6-dicarboxylic acid and pyromellitic acid (linkers) to tailor their morphological evolution and electrochemical properties. This strategic modulation was found to directly influence electrochemical behavior. Among the synthesized materials, X2 (PDC_0.75PMA_0.25-MOF) exhibited the most favorable characteristics, achieving low ESR (0.72 Ω) and electrochemical efficiency (demonstrating 694.3 C g^-1 at 3 mV s^-1 and 576.6 C g^-1 at 0.6 A g^-1) in a three-electrode cell configuration. To further evaluate its real device potential, a battery-supercapacitor hybrid device (X2//AC) was fabricated, demonstrating a remarkable specific capacity of 298.1 C g^-1 at 1.4 A g^-1, a high specific energy of 70.3 W h kg^-1 at a power density of 1190 W kg^-1, and good cycling stability (98.5% retention after 5000 cycles). These findings open a new pathway for future research on bi-linker-driven MOF design, providing a novel strategy for enhancing electrochemical performance and advancing next-generation energy storage applications.