ZIF-8-Decorated Lychee-like ZnO for Highly Sensitive Ammonia Detection at Room Temperature

The integration of materials can generate synergistic effects, forming the core concept of a new generation of multifunctional applications. In particular, the integration of the ZnO structure with the zeolite imidazolate framework-8 (ZIF-8) has been shown to enhance gas selectivity, which is mainly achieved through the molecular sieving effect of the specific-sized porous structure of ZIF-8. In this work, a room-temperature ammonia (NH3) gas sensor based on ZnO/ZIF-8 composites was fabricated via a combination of hydrothermal synthesis, templating, and drop-casting methods. By tuning the concentration of 2-methylimidazole, the ZIF-8 content was optimized, and the ZnO/ZIF-8–2 sensor exhibited robust NH3 sensing performance at room temperature. The sensor exhibited outstanding sensitivity toward NH3 (150.16@100 ppm), approximately 16 times that of pure ZnO sensor, with a rapid response/recovery time (14.5 s/1.6 s). Furthermore, the sensor showed remarkable selectivity, repeatability, and humidity resistance. This improvement is attributed to the increased content of oxygen vacancies and adsorbed oxygen species, high carrier density, the unique lychee-like morphology and large specific surface area, and the synergistic effect of the ZnO/ZIF-8 heterojunction. This study provides a promising strategy for the efficient detection of NH3 at room temperature using ZIF-8-based hybrid materials.