Redox-active covalent organic frameworks for supercapacitors: A molecular-level design and integration approach

Supercapacitors (SCs) represent critical electrochemical energy storage technologies, yet breakthrough performance requires revolutionary electrode materials with precise molecular engineering. Developing electrodes with high capacitance is a direct and efficient approach to enhance the energy storage capability of supercapacitors. Organic materials, whose molecular structures can be diversely designed to achieve high pseudocapacitance through redox-active units in their backbone, serve as promising electrode candidates for supercapacitors. Covalent organic frameworks (COFs) offer unprecedented opportunities for atomic-level customization through structural tunability, exceptional porosity, and modular architecture. This review establishes the first systematic redox-center classification framework for COF-based SC materials, directly linking molecular structure to electrochemical performance. This review comprehensively categorize COF architectures based on redox-active centers: carbonyl/hydroxyl frameworks, heteroatom-engineered structures, and radical-stabilized systems. Subsequently, this review examines diverse COF-based electrodes including 2,6-diaminoanthraquinone, azodianiline, naphthalene, nitrogen-rich (pyridine, triazine, benzimidazole, triphenylamine), and thiol-based platforms. A distinctive contribution involves elucidating interfacial engineering strategies through systematic COF integration with carbon allotropes, metals, MXenes, and conductive polymers. This review establishes quantitative structure-performance relationships governing charge transfer mechanisms and capacitive behavior at engineered interfaces. Additionally, this review presents the first comprehensive analysis of COF carbonization pathways, revealing transformation mechanisms enabling tailored porosity and conductivity optimization. This work identifies critical technological challenges and presents innovative solutions for scalable synthesis, enhanced stability, and application-specific optimization. The molecular-level design framework and integration strategies establish a roadmap for next-generation COF-based energy storage systems, positioning these materials at the forefront of sustainable electrochemical technologies.