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

• Published in: Angewandte Chemie International Edition 2023-05, Vol.62 (19), p.e202301440-n/a
• Main Authors: Mei, Aohan, Chen, Wen, Yang, Zifan, Zhou, Min, Jin, Wei, Yang, Shuang, Chen, Keqiang, Liu, Yueli
• Format: Article
• Language: English
• Subjects: Covalent Organic Framework; Deformation; Flexible Devices; Human body; Humidity Sensing; Hygrometers; Intermediates; Reconfiguration; Relative humidity; Respiration Monitoring; Room temperature; Sensitivity; Water Adsorption; Water chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202301440

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. A flexible COF‐5 film is synthesized on PI substrate by a vapor‐assisted conversion method and used to fabricate a humidity sensor. The sensor shows resistance response to 11 %–98 % RH over 4 orders of magnitude and maintains a linear relation even when bent at 180°. Simulations are applied to reveal the intermolecular reconfiguration mechanism in humidity sensing. The superior sensitivity makes COF‐5 films a potential candidate for human respiration monitoring.