Molecular-level engineering of heteroatom-functionalized 2D covalent organic frameworks for highly efficient supercapacitor performance

Abstract

The design of heteroatom-containing COFs as electrode materials for energy storage applications has received limited attention. The redox activity of heteroatoms, combined with high conductivity and ordered porosity, positions COFs as promising candidates for advanced supercapacitors and other high-performance electrochemical devices. Herein, we report two heteroatom-enriched covalent organic frameworks consisting of triazine and benzotrithiophene moieties as electrode materials for high-performance supercapacitors. The presence of heteroatoms affords highly crystalline and porous COFs with effective π-conjugation, redox activity, and high electronic conductivity, enabling efficient ion diffusion and charge transport. Both heteroatom-functionalized COFs exhibited excellent performance as supercapacitor electrodes. Interestingly, the benzotrithiophene-based COF delivered outstanding performance, achieving a high specific capacitance of 916 F g⁻¹ at a current density of 1 A g⁻¹, along with excellent rate capability and cycling retention of 91.9% after 10 000 cycles. Furthermore, an asymmetric supercapacitor device exhibited a specific capacitance of ∼72 F g⁻¹ at 1 A g⁻¹, with maximum energy and power densities of 22.5 Wh kg⁻¹ and 750 W kg⁻¹, respectively. The high efficiency and durability of the COF can be attributed to the π-conjugated, sulfur-rich benzotrithiophene moiety, which provides high redox activity, effective π-delocalization, and facile ion transport, thereby enabling heteroatom-based charge storage mechanisms. This work highlights that molecular-level engineering of COF structures via heteroatom functionalization is an effective approach for developing next-generation electrode materials for energy storage devices.