Rod-Flower-Like ZnO@ZIF-67: A Formaldehyde Gas Sensor Material with High Sensitivity and Selectivity

Formaldehyde vapor (CH 2 O) is a well-known hazardous gas. Long-term exposure to high concentrations of CH 2 O can cause chronic respiratory diseases in humans and increase the risk of cancers such as leukemia and nasopharyngeal cancer. Zeolite imidazolic frame-67 (ZIF-67) has a high specific surface area and porosity; therefore, it can be used to prepare gas-sensitive materials. In this study, rod-flower-like ZnO was obtained by activation of the rod ZnO using 2-methylimidazole. The ZIF-67-coated rod-flower-like ZnO was then used to synthesize ZnO@ZIF-67 (ZZ67). Experimental and theoretical analyses showed that the ZIF-67 on the ZZ67 surface provided abundant active sites for pure ZnO, which helped to capture target gas molecules more quickly in the experimental atmosphere and realize susceptible detection. Moreover, ZZ67 had a high response (1210) to 500 ppm of CH 2 O at room temperature (~25 ℃), which was 4.8 times the response of activated ZnO (251). Furthermore, owing to the high hydrophobicity of ZIF-67, ZZ67 was mainly unaffected by humidity. Overall, ZZ67 exhibited good selectivity, a high response to CH 2 O, and low sensitivity to high relative humidity.