Cauliflower-like Sn-ZnO/ZIF-67 for highly sensitive and selective NH3 detection, and monitoring freshness of soy products

Accurate detection of ammonia (NH 3 ) is a key indicator for evaluating the deterioration of high-protein foods and is of great significance for food safety. In this study, we modified Sn-ZnO using a Co-based metal–organic framework (MOF) material (ZIF-67) to prepare cauliflower-shaped Sn-ZnO/ZIF-67 (SZZ67) for NH 3 sensors at room temperature (25 °C). By regulating Co 2+ , it was found that the sensor's response to NH 3 decreased with the increase in Co 2+ content, while the desorption ability was significantly enhanced. When the mass ratio of Sn-ZnO to the added C 4 H 6 CoO 4 ∙4H 2 O was 1:1, its response was 13.46 times that of Sn-ZnO, the response/recovery time was 63.78/7.99 s, and good moisture resistance was observed. Density functional theory (DFT) confirmed that SZZ67 can adsorb more NH 3 and release more conductive electrons, thereby increasing its response value. The sensors prepared using SZZ67 could more effectively monitor NH 3 , which is applicable for monitoring the freshness of soy products.