Metal-Organic Frameworks as Room Temperature Chemiresistive Ammonia Gas Sensing Material: A Review

The growing demand for reliable, real-time detection of ammonia (NH₃) has accelerated the development of chemiresistive gas sensors, while conventional semiconductors employed as sensing materials in chemiresistive sensors remain constrained by limited selectivity and high operating temperatures (typically 200-400 °C). Among the emerging porous materials, metal-organic frameworks (MOFs) have attracted significant attention as room-temperature NH₃ sensing materials owing to their structural tunability, enabling precise control over pore chemistry, functionality, and metal centers. However, a comprehensive study specifically focused on MOF-based chemiresistive NH₃ sensors operating at room temperature remains limited. This review critically targets the investigation of pristine MOFs, conductive MOFs, and MOF-based composites for NH₃ sensing, with an emphasis on sensing mechanisms, structure-property-performance relationships, stability, selectivity, and environmental effects. Furthermore, rational design strategies and prospects are discussed to provide guidelines for the development of next-generation high-performance room-temperature NH₃ chemiresistive sensors.