Single‐Crystal Covalent Organic Frameworks Isomers With Atomic‐Level Engineered Nitrogen Sites for Efficient Zn‐Iodine Batteries

ABSTRACT Single‐crystal covalent organic frameworks (COFs) isomers offer an ideal platform for understanding the structure‐function relationship, yet their development remains underexplored. Herein, we reported two single‐crystal COFs isomers (4,4′‐COF and 6,6′‐COF) with precisely atomic‐level engineered nitrogen‐site for COF‐based Zn‐Iodine batteries. The isomerism of nitrogen microenvironments in 4,4′‐COF and 6,6′‐COF leads to their significantly different polyiodide confinement capabilities. When employed 6,6′‐COF as an iodine species host in Zn‐Iodine batteries, 6,6′‐COF‐based electrode materials showed a high specific capacity of 287 mAh/g (1.7 times of 4,4′‐COF counterpart), along with exceptional cycling stability over 6000 cycles. Combined with in situ spectroscopic study and theoretical calculations confirmed that the optimized pyridinic nitrogen configuration in 6,6′‐COF can effectively immobilize polyiodide species, thereby suppressing the shuttle effect. This work established atomic‐level nitrogen‐site engineering in single‐crystal COFs as a new paradigm for elucidating and exploiting structure‐activity relationships in energy storage.