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

The practical application of aqueous zinc-iodine (Zn-I₂) 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-NO₂) outperforms in both I₂ 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-NO₂-based Zn-I₂ 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 I₂ utilization. These findings are further supported by in situ Raman and UV-vis spectroscopy, which identified a dominant I^‒/I₅ ^‒ 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-I₂ batteries, offering an effective dual strategy to enhance iodine utilization and mitigate the shuttle effect.