Electronically Modulated TpPa COF as a High‐Performance Iodine Host for Zn–I 2 Batteries

Abstract The practical application of aqueous zinc–iodine (Zn–I 2 ) batteries is hindered by poor iodine utilization and limited cycling stability, primarily due to the shuttle effect of soluble polyiodide species. In this study, side‐group engineering is employed to modulate the electronic structure of hexagonal porous TpPa covalent organic frameworks (COFs). Among the engineered COFs, the nitro‐functionalized TpPa COF (TpPa‐NO 2 ) outperforms in both I 2 utilization and cycling stability, achieving a high specific capacity of ≈183 mAh g ‒1 at 0.1 A g ‒1 and a remarkable capacity retention of 84.3% after 10 000 cycles at 5 A g ‒1 . Notably, the TpPa‐NO 2 ‐based Zn–I 2 batteries maintain mitigated polarization and stable operation under harsh conditions, including low temperatures (−5 °C) and high iodine loading (≈15 mg cm ‒2 ). Theoretical simulations reveal that the electronic modulation reduces the TpPa COF's band gap and enhances the affinity for polyiodide species, thus improving the I 2 utilization. These findings are further supported by in situ Raman and UV–vis spectroscopy, which identified a dominant I ‒ /I 5 ‒ redox pathway and confirmed suppression of polyiodide dissolution. This work underscores the promise of electronically tailored COFs as advanced cathode hosts for long‐life Zn‐I 2 batteries, offering an effective dual strategy to enhance iodine utilization and mitigate the shuttle effect.