Tailoring Redox‐Active Interfaces‐Oriented Bi ₂ O ₃ /g‐C ₃ N ₄ Heterostructures Engineered From CTAB‐Assisted Bi‐MOF for High‐Energy Supercapacitive Energy Storage

Metal organic framework (MOF) derived heterostructure provides a versatile platform for elucidating and optimizing charge storage mechanisms in high‐performance supercapacitors. Herein, a β‐Bi 2 O 3 /g‐C 3 N 4 composite is obtained through controlled thermal conversion of Bi‐based MOF in the presence of CTAB surfactant, which plays a critical role in regulating nucleation, interfacial coupling, and pore evolution. The resulting architecture integrates redox‐ active β‐Bi 2 O 3 with the chemically stable and conductive g‐C 3 N 4 matrix, enabling concurrent surface–confined pseudocapacitive reactions. Enhanced interfacial charge transfer and shorter diffusion pathways collectively promote rapid electrochemical kinetics, as evidenced by the high specific capacitance of 411.2 Fg −1 at a current density of 1 Ag −1 . When configured as an asymmetric supercapacitor under PVA/Na 2 CO 3 gel electrolyte, the β‐Bi 2 O 3 /g‐C 3 N 4 //graphite device achieves a specific capacity of 217.3 Cg −1 , high energy density of 54.4 Wh/kg, and high power density of 9000 W/kg with capacitance retention of 96% after 20,000 cycles, reflecting efficient utilization of both faradic and nonfaradic processes over a widened operating voltage (1.8 V). The device is further capable of powering three blue light‐emitting diodes for 6 min, demonstrating practical energy delivery with sustainability. This work illuminates the role of surfactant‐assisted MOF in oxide transformation in governing charge storage behavior and provides mechanistic insights for the rational design of next‐generation supercapacitor electrodes.