Interfacial Engineering of Redox-Active Covalent Organic Frameworks/Graphene Hybrids for High-Performance...

Covalent organic framework (COF)/graphene hybrids are promising electrode materials for next-generation supercapacitors, yet critical challenges persist: the structure-property relationship of the molecular structure of COFs governing the COF/graphene interface remains poorly understood. Herein, we employ electrochemically exfoliated graphene (EG) as a soft template that combines high crystalline quality with solution processability to direct the uniform in situ growth of structurally distinct COFs along its two-dimensional (2D) basal plane. This strategy ensures high composite conductivity, promotes efficient charge transfer via π-π interactions between graphene and COF layers, and enhances the accessibility of redox-active sites, which are key aspects for achieving superior electrochemical performance. We synthesized four different COFs: Tp-TAPT, Tp-TAPB, Tb-TAPT, and Tb-TAPB, using 2,4,6-triformylphloroglucinol (Tp) or 1,3,5-triformylbenzene (Tb) with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) or 1,3,5-tris(4-aminophenyl)benzene (TAPB), which are systematically constructed to introduce two structural variables: β-ketoenamine versus imine linkages and triazine versus non-triazine aromatic units. They were subsequently grown in situ on EG to achieve the corresponding hybrids (denoted Tp-TAPT@G, Tb-TAPT@G, Tp-TAPB@G, and Tb-TAPB@G, respectively). Among them, Tp-TAPT@G, which combines β-ketoenamine and triazine units, exhibits pronounced multiple redox features, favorable interfacial π-π interactions with EG, and a more uniform and continuous 2D growth morphology. Tp-TAPT@G delivers a volumetric capacitance of 261.31 F/cm3 at a current density of 0.3 mA/cm2 and retains 76.38% of this value at 5.0 mA/cm2, portraying excellent rate capability. Moreover, a planar supercapacitor device assembled from this composite demonstrates outstanding high-rate performance, underscoring its promise for fast-charging applications. This study elucidates how the COF structure regulates interfacial behavior in COF/graphene composites, providing a foundation for the rational design of high-performance energy storage materials.