Sulfonated hypercross-linked porous organic polymer based humidity sensor

Humidity sensors are of great significance in industry, agriculture and human activities, and many nanomaterials are already used for humidity sensing. Linear ionic polymers with hydrophilic groups have exhibited good humidity detection performance because they can adsorb water and then dissociate charged carriers. However, it suffers from the instability under high relative humidity that caused by polymer chain swelling and disengagement. To overcome this shortage, in this work, a new sensor based on hypercross-linked porous organic polymer (POP) with sulfonic acid group was fabricated to humidity detection in wide humidity range. The POP with strong covalent bonds exhibits remarkable chemical and thermal stability, and sulfonic acid group in the pore can act as fully accessible active site to enhance its ability to adsorb water. The obtained sensor shows high response (∼77) in a wide relative humidity range (11%−95% RH), short response/recovery time (9 s/21 s) and good stability. Complex impedance curves and density functional theory have been carefully investigated to understand its sensing mechanism. This work provides a new direction for the development of the impedance-type humidity sensitive materials in subsequent research and practical applications.