Sensitive humidity sensors based on ionically conductive metal-organic frameworks for breath monitoring and non-contact sensing

Abstract

Metal-organic frameworks (MOFs) are functional materials with high surface areas and good crystallinity. Using a modified liquid-interface spraying method, the unique ionically conductive MOFs (IC-MOFs) are developed, with metal ions as charge carriers. In this study, capacitive humidity sensors based on IC-MOFs are fabricated and applied in breath monitoring and non-contact sensing for the first time. By rational tuning of metal ions and organic ligands, a series of IC-MOFs humidity sensors are prepared and compared comprehensively. The humidity sensors exhibit high sensitivity, wide sensing range, and short response/recovery time. Additionally, the devices can maintain good sensing performance under extremely low and high humidity, showing excellent stability. The decent sensing performance endows the sensor various potential applications, such as humidity detection in daily life and a wide range of applications in flexible electronics. This study would provide a new approach for the development of humidity sensing materials.