α‐Iminonitrile‐Linked Covalent Organic Framework synthesized by Ehrlich‐Sachs Reaction as a promising Cathode for Sodium‐Ion Batteries

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.