Hygrosensitive Dynamic Covalent Organic Framework Films: Harnessing Molecular Rotors for Moisture‐Driven Actuation in Wearable Health Monitoring

Dynamic covalent organic frameworks (COFs) offer a promising platform for bioinspired soft actuators, yet transitioning their typical microcrystalline or single crystalline morphology to a flexible film suitable for wearable technology applications still remains a grand challenge. Herein, aiming at this issue, this work synthesizes an innovative class of hygrosensitive COF films, denoted as JNU‐ hygro COF, with superior mechanical strength, chemical stability and tunable thickness from nanometer to micrometer scales through solution‐processable sol‐gel method. These JNU‐ hygro COF films display exceptional moisture‐driven actuation capabilities through modulating the intramolecular hydrogen bonds, which act as specific locks that open and close the molecular rotor of N─N bond responding to guest molecules, within the unique azine‐pyridine molecular skeleton. By integrating these new JNU‐ hygro COF films into a portable respiratory monitoring system, a proactive and preventive solution for diagnosing and managing respiratory disorders such as sleep apnea and asthma has been provided.