Study of Intermolecular Reconfiguration of Flexible COF‐5 Film and Its Ultra‐high Chemiresistive Humidity Sensitivity

Abstract Recently, abundant active materials are developed to achieve the wearable detection of human body humidity. However, the limited response signal and sensitivity restrict further application due to their moderate affinity to water. Herein, we propose a flexible COF‐5 film synthesized by a brief vapor‐assisted method at room temperature. Intermediates are calculated by DFT simulation to investigate the interaction between COF‐5 and water. The adsorption and desorption of water molecule result in a reversible deformation of COF layers while creating new conductive path by π–π stacking. The as‐prepared COF‐5 films are applied to the flexible humidity sensors, exhibiting a resistance change in 4 orders of magnitude with remarkable linear relation between log function of resistance and relative humidity (RH) in 11 %–98 % RH range. Applications including respiratory monitoring and non‐contact switch are tested, providing a promising prospect for the detection of human body humidity.