A Self‐Adaptive Hydrogen‐Bonded Organic Framework for Long‐Term Low‐Temperature Sodium‐Ion Storage

ABSTRACT Sodium‐ion batteries (SIBs) are gaining limelight for research owing to their large‐scale, all‐climate energy storage, yet their practical application remains plagued by unreliable performance at low temperatures. A key reason is the lack of cathode materials that can preserve both structural stability and ion‐transport kinetics under deep subzero conditions. Here, we report a hydrogen‐bonded organic framework (HOF) cathode for SIBs, HOF‐PZQ, with a rigid π‐conjugated backbone reinforced by an extensive network of directional O─H···O hydrogen bonds. HOF‐PZQ combines framework‐level structural coherence with adaptive supramolecular response, enabling stable Na + storage under deep subzero conditions where conventional organic cathodes often suffer from kinetic degradation and structural instability. As a result, HOF‐PZQ delivers stable cycling for 5000 cycles at 1 A g −1 at room temperature. Even at −40°C, it achieves a reversible capacity of 105 mAh g −1 , with 98% capacity retention after 1000 cycles at 100 mA g −1 . We demonstrate that Na + insertion and extraction occur at the C═N redox sites and are accompanied by reversible reorganization of the hydrogen‐bond network, which accommodates local electrostatic stress without loss of long‐range crystallinity. This work highlights HOFs as promising cathodes for reliable sodium‐ion storage in harsh cold environments.