Growth of Nanostructured Antibacterial Zeolitic Imidazolate Framework Coatings on Porous Surfaces

Morphological tailoring of crystalline nanomaterials such as zeolitic imidazolate frameworks (ZIFs) is essential for various applications, including oil-water separations, molecular sieving, and antibacterial applications. However, precise control of the morphology of these crystals is challenging. Herein, the morphological evolution map of ZIF-L to ZIF-8 nanocrystals on porous polymer supports was constructed in terms of ethanol content and processing temperature variation. Subsequently, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analyses demonstrated that an increase in the temperature in low ethanol content led to the formation of ZIF-L nanocrystals with decreased lateral size and increased crystal thickness. Comparatively, increased ethanol content typically increases crystal thickness with a greater degree of crystal intergrowth. However, an increase in both parameters exhibited a preferential formation of its three-dimensional (3D) structural analog, ZIF-8, and consequently resulted in a ZIF-L/ZIF-8 mixed phase at midrange temperatures (50-60 degrees C) and ethanol content (10 v/v%). The mixed phase demonstrated the stacking of ZIF nanosheets, with the morphology change significantly impacting the properties of the ZIF nanocrystals. As one example, the antibacterial performance of the as-prepared materials of different morphologies was analyzed to investigate the morphological impact on antibacterial efficiency. It was found that crystals with reduced crystal size and increased surface area resulted in improved antibacterial performance. Meanwhile, the nanostructured ZIF coating's hydrophilicity and hydrostability were also enhanced with increased ethanol content and elevated temperatures. Overall, we reported a very useful method to conveniently control the morphology of ZIF nanocrystals for improved applications.