Understanding the Growth of ZIF-8 Thin Film and Its Room Temperature Carbon Dioxide Sensing via Quartz Crystal Microbalance.

Metal-organic frameworks (MOFs), particularly zeolitic imidazolate frameworks (ZIFs), have emerged as promising materials for gas sensing applications due to their high surface area and tunable porosity. This study presents a systematic chemical bath deposition (CBD) approach for fabricating ZIF-8 films with precisely controlled thicknesses of up to 2.5 μm on functionalized surfaces. Film particle evolution and growth mechanisms were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with in situ growth monitoring. Imidazolate achieved a uniform growth rate of 95 nm per cycle, and imidazolate-surface interfacial coordination was elucidated. By integrating these controllable ZIF-8 films with a quartz crystal microbalance (QCM), we developed a gravimetric gas sensor that demonstrated enhanced CO2 adsorption capacity with increasing film thickness and achieved a detection limit of 0.5%. This systematic approach to controlling the ZIF-8 film thickness enables precise quantification of gas absorption, advancing the development of high-precision gas sensors for environmental monitoring applications.