Metal-organic framework-based gas sensors: fabrication, mechanisms, and applications

Gas-sensing technologies facilitate the early detection and prediction of unforeseen future events by tracking surrounding invisible and instantaneous molecular information, which is critical for applications in agriculture, medicine, chemical process control, and environmental monitoring. Recent advancements in metal-organic frameworks (MOFs), which are characterized by large surface areas, rich porosity, tunable pore sizes and geometries, and distinctive surface chemical properties, have paved the way for the development of next-generation gas sensors. The types and functions of MOFs in gas sensors have undergone significant advancements, particularly in terms of low operating temperatures, high sensitivity, and selectivity. However, a systematic analysis correlating the transduction mechanism and morphological structures of various MOF-based gas sensors is still lacking, in addition to a comprehensive summary of the most recent MOF-based gas sensors. This review provides a comprehensive overview of the latest advancements in MOF-based gas sensors, with a focus on their fabrication strategies, sensing mechanisms, and applications. Examples of MOF-based sensors include chemiresistive, field-effect transistor, Kelvin probe, capacitive, and optical gas sensors. Moreover, MOF-based gas sensors have been extensively investigated for applications in chiral recognition and flexible devices. Furthermore, we discuss the limitations of various MOF-based gas sensors developed to date and the corresponding solutions. Finally, we present our perspectives on the challenges and opportunities encountered in the advancement and practical applications of MOF-based gas sensors.