Capacitive gas sensors based on a ZIF-67/PAN nanofiber membrane to detect volatile organic compounds

Abstract

Metal-organic frameworks (MOFs) are potentially useful in gas-sensing applications. However, MOFs are available in powder form, hindering their direct application. Moreover, MOF-based gas sensors use ceramic substrates, which have poor mechanical flexibility. To address these limitations, a zeolitic imidazolate framework (ZIF-67) was uniformly applied to the surface of polyacrylonitrile (PAN) electrospun nanofibers by in situ growth. The resulting ZIF-67/PAN nanofiber membrane (NM) was used as a dielectric layer material for a capacitive gas sensor. Our results show that in situ growth can improve the degree of dispersion of MOFs in the powder state and increase the specific surface area of the material. The ZIF-67/PAN NM maintained the flexibility and air permeability of the PAN NM, which improved the response speed and application range of the sensor. Additionally, the ZIF-67/PAN-based capacitive gas sensor exhibited excellent sensing performance (250–1250 ppm) for volatile organic compounds (VOCs), such as methanol, ethanol, and acetone, at normal atmospheric temperatures. Our results indicate that ZIF-67 selectively adsorbs gas molecules through its pores; therefore, the closer the diameter of the gas molecules is to the pore diameter of ZIF-67, the stronger is the adsorption effect.