Hypervalent Iodine-Mediated Stereotactic Amidation Enables COF-to-COF Transformation for Supercapacitors

Imine-linked covalent organic frameworks (iCOFs) emerge as promising candidates for next-generation energy storage systems, attributed to their high crystallinity and tailorable pore sizes, but the inherent imine bond reversibility-induced poor chemical stability hinders their application in redox electrolytes. Therefore, precise COF-to-COF transformation of iCOFs aimed at enhancing their stability while retaining crystallinity and structural integrity is highly desirable yet remains a significant challenge. Here, we report a hypervalent iodine-mediated stereotactic amidation strategy for achieving COF-to-COF transformation, by which the interfacial stability and diffusion kinetics of the transformed amide COFs (BI-aCOF) were enhanced while well preserving the intrinsic morphological structure and high crystallinity of the precursor BI-iCOF. Notably, this stereotactic amidation strategy can be further extended to fabricate a broad spectrum of aCOFs including AI-aCOFs and AII-aCOFs. All the transformed aCOF-based KI-enhanced supercapacitors delivered ultrahigh specific capacitance, superior energy density, and long cycling lifespan, far surpassing that of the parent iCOF- and previously reported COF-based aqueous supercapacitors. Such remarkable improvements originate from the inherent advantages of amide linkages over pristine imine bonds, including enhanced hydrophilicity, efficient charge delocalization, and improved interfacial acid resistance. These favorable characteristics accelerate ion diffusion kinetics and strengthen the accommodation capacity toward polyiodide species within the KI-H₂SO₄ electrolyte. This work presents a feasible and universally applicable COF-to-COF transformation strategy for advanced redox-boosted electrochemical energy-storage systems.