Proton‐Tautomerism Drives Redistribution of Electron Cloud Density in Covalent Organic Framework for Efficient Sodium‐Ion Storage

Abstract

ABSTRACT Proton tautomerism, a ubiquitous phenomenon involving the dynamic interconversion of structural isomers through proton migration, has seldom been utilized in electrode design. One known example of this untapped potential is the imine‐enamine (─NH─/═N─) equilibrium in conjugated heterocycles. Herein, this reversible process is harnessed to regulate charge transport in covalent organic frameworks (COFs). Two π‐conjugated COFs, HATBQ and HATPT, were constructed via nucleophilic aromatic substitution (SNAr), which integrate dense C═N/C═O redox‐active sites into chemically stable skeletons. The conjugated imine bonds, formed via nucleophilic aromatic substitution, enable the formation of an extensive network of intramolecular hydrogen bonds. This network enhances the crystallinity of the COFs without compromising the reversible proton tautomerism. These combined characteristics endow the COFs, particularly HATPT, with exceptional long‐term cycling stability and rate performance. As a result, HATPT delivers outstanding durability in Sodium‐ ion batteries (SIBs), retaining 225 mAh g −1 after 5000 cycles at 10 A g −1 , and exhibits strong compatibility in full‐cell configurations with Na 3 V 2 (PO 4 ) 3 (NVP). This tautomerism‐driven electronic modulation significantly lowers the activation energy for redox reactions, thereby facilitating efficient Na + storage kinetics.