Rational Integration of Electron-Positive Linkages into Covalent Organic Framework Electrode for High-Performance Aqueous Zinc-Ion Batteries

Covalent organic frameworks (COFs) with tailored functional groups represented promising electrode materials for aqueous zinc-ion batteries (AZIBs). However, while prevailing research on linker and vertex chemistries─especially enhancing redox-active sites and electron conduction─the potential of linkage chemistry in regulating Zn2+/H+ transport kinetics remained fundamentally underexplored. Herein, a covalent organic framework (HPP-COF) featuring hexaazatriphenylene as redox-active vertex center and electron-positive pyridinamine linkage was fabricated as the electrode material for AZIBs. The high-density redox-active sites, coupled with effective electron delocalization and intermolecular π–π interactions, collectively ensure substantial and stable H+/Zn2+ storage. Furthermore, the electron-positive nature of the pyridinamine linkage modified the local electronic environment to accelerate redox kinetics at the electron-negative hexaazatriphenylene center. Consequently, HPP-COF achieved a high reversible capacity (309 mAh g–1 at 0.025 A g–1), outstanding rate performance (57 mAh g–1 at 5 A g–1), and exceptional cycling stability with 80.1% capacity retention after 6000 cycles at 2 A g–1. Mechanistic studies further revealed a multistep co-storage mechanism of Zn2+ and H+ with the C═N groups, involving the initial coordination of Zn2+ followed by the binding of H+. This work provides new insights into the rational linkage design of COF electrodes for enhancing the electrochemical performance.