α‐Iminonitrile‐Linked Covalent Organic Framework Synthesized by Ehrlich–Sachs Reaction as a Promising Cathode for Sodium‐Ion Batteries

Abstract Linkages represent the key feature to affect the properties of covalent organic frameworks (COFs), where chemical perturbation on the linkage microenvironment often leads to a remarkable impact on their applications. Following this strategy, we directly functionalized the imine linkage with a cyano group to form an α‐iminonitrile‐linked COF (CityU‐48) by employing a classic Ehrlich–Sachs reaction between tris‐(4‐nitrosophenyl) amine (TPA‐3NO) and 1,4‐phenylenediacetonitrile (Ph‐2CN). However, this perturbation makes CityU‐48 susceptible to crystallization due to the steric hindrance and polarity induced by extra cyano groups. By taking advantage of the bipolar redox‐active nature, CityU‐48 delivered a discharge capacity of 139 mAh g −1 at the current density of 100 mA g −1 when employed as a cathode in sodium‐ion batteries. These research efforts motivate the design of new linkages to explore their roles in COFs at the atomic level.