Scalable, thermally stabilized MOF-graphene fibers with hierarchical porosity for high-performance energy storage devices

Abstract

Next-generation energy storage devices require electrodes that combine high charge storage capacity, mechanical robustness, and scalable fabrication. Here, we present a new class of thermally stabilized, hierarchically porous hybrid fibers integrating copper benzene tricarboxylate (Cu-BTC) metal–organic frameworks (MOFs) with liquid crystalline graphene oxide, addressing long-standing challenges in MOF processing for fiber-based architectures. Incorporating Keggin-type phosphotungstic acid polyoxometalate enhances the thermal stability of the Cu-BTC framework, enabling wet spinning and thermal reduction to produce conductive MOF-reduced graphene oxide hybrid fibers. In addition to providing high surface area and hierarchical porosity, the MOF structure introduces redox-active sites that contribute to pseudocapacitance, further improving charge storage. The resulting fibers exhibit outstanding electrochemical performance in a symmetric two-electrode configuration, delivering a gravimetric capacitance of 476.9 F g⁻¹ at 0.77 A g⁻¹ and maintaining 307.7 F g⁻¹ even at a high current density of 7.69 A g⁻¹, demonstrating remarkable rate capability. The fibers also show excellent cycling stability, with 96.7% capacitance retention over 4000 cycles. Moreover, the hybrid device achieves an areal energy density of 29.9 μWh cm⁻² at a power density of 0.35 mW cm⁻², and retains 19.29 μWh cm⁻² even at a higher power density of 3.47 mW cm⁻², significantly outperforming many previously reported fiber-based supercapacitors. Beyond electrochemical function, the fibers demonstrate exceptional mechanical strength (Young's modulus >42 GPa), offering a rare combination of durability and performance. This work establishes a versatile platform for integrating MOFs into flexible, high-performance, and scalable fiber-based energy storage devices.