Metal–organic framework-derived ultra-microporous bismuth oxide synchronizing energy density and stability in symmetric supercapacitors

The development of bismuth oxide (Bi₂O₃) for supercapacitor applications is often limited by its intrinsically low electrical conductivity and structural instability during cycling. Herein, a metal–organic framework (MOF)-derived strategy is employed to engineer ultra-microporous Bi₂O₃ architectures with tailored structural and electrochemical properties. Through a controlled solvothermal synthesis followed by calcination using terephthalic acid as an organic linker, a hierarchically porous Bi₂O₃ structure is obtained with an enhanced surface area of 117 m² g⁻¹ and dominant ultra-micropores centered at 0.42 nm. The engineered porous framework promotes efficient electrolyte infiltration and improves redox accessibility, resulting in a high specific capacitance of 876 F g⁻¹ at 0.5 A g⁻¹ in a three-electrode configuration. When assembled into a symmetric two-electrode supercapacitor operating within a 0–0.6 V window, the MOF-derived Bi₂O₃ electrode delivers a device-specific capacitance of 950 F g⁻¹, achieving a maximum energy density of 47.2 Wh kg⁻¹ at a power density of 150 W kg⁻¹. The device maintains 75.3% capacitance retention after 10 000 charge/discharge cycles with a coulombic efficiency of 81.4%. These findings demonstrate that MOF-assisted structural engineering effectively enhances ion transport pathways and electroactive surface utilization, offering a viable strategy for improving the electrochemical performance of metal oxide-based supercapacitors.