In Situ Synthesis of Hierarchical Co(CO 3 ) 0.5 (OH)·0.11H 2 O@ZIF-67/WO 3 With High Humidity Immunity and Response to H 2 S Sensing.

H 2 S gas sensors with facile preparation, low detection limits, and high selectivity are crucial for environmental and human health monitoring. However, it is difficult to maintain a high response of H 2 S gas sensors under high humidity in practical applications. To face this dilemma, a layer-by-layer growth method is applied to in situ prepare a nanostructured Co(CO 3 ) 0.5 (OH)·0.11H 2 O/WO 3 coated by a hydrophobic hierarchical ZIF-67 as the H 2 S sensor. This novel composite exhibits excellent humidity immunity without sacrificing the excellent sensitivity and selectivity of H 2 S. At a low operating temperature of 90 °C, a remarkable response value of 1052.3 to 100 ppm H 2 S has been achieved, which is 779 and 9.36 times higher than that of pure WO 3 and Co(CO 3 ) 0.5 (OH)·0.11H 2 O/WO 3 , respectively. More importantly, an 82.2% relative response value remains at a high humidity of 75%RH. The sensing mechanisms are investigated using gas chromatography-mass spectrometry (GC-MS), which revealed that the reaction products are H 2 O and SO 2 . The high humidity immunity and fast response of the Co(CO 3 ) 0.5 (OH)·0.11H 2 O@ZIF-67/WO 3 demonstrate the layer-by-layer in situ synthesis method holds the potential application for the development of high-performance WO 3 -based H 2 S sensors.