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.