Synthesis, Characterization, Density Functional Theory Study, Antibacterial Activity and Molecular Docking of Zeolitic Imidazolate Framework-8

In this study, Zeolitic Imidazolate Framework-8 (ZIF-8) nanomaterials were synthesized using a co-precipitation one-pot method that uses ethanol, methanol, and water as solvents for the precursors (2-methylimidazole and Zinc nitrate hexahydrate), resulting in yields of 66.77%, 73.14%, and 68.12%, respectively. The as-synthesized ZIF-8 nanomaterials were thoroughly characterized by X-ray diffraction analysis, transmission electron microscopy, ultraviolet–visible spectroscopy, and Fourier-transform infrared spectroscopy. The X-ray diffraction analysis showed that the crystallite size of ethanol-based ZIF-8 (24.76 ± 1.67 nm) was smaller than those synthesized in water (26.92 ± 1.89 nm) and methanol (31.39 ± 1.03 nm). However, methanol-based ZIF-8 exhibited lower crystallinity (85.93%) than water-based ZIF-8 (91.48%) and ethanol-based ZIF-8 (92.71%). Zeta potential studies revealed that ethanol-based ZIF-8 had a larger surface charge (+37 mV) than water-based ZIF-8 (+35 mV) or methanol-based ZIF-8 (+24 mV). Transmission electron microscopy analysis confirmed particle sizes of 54.35 ± 2.11 nm for ethanol-based ZIF-8, 57.91 ± 2.26 nm for water-based ZIF-8, and 63.25 ± 4.12 nm for methanol-based ZIF-8. Thermogravimetric analysis indicated thermal stability up to 800 °C, with mass losses of 55.98% for ethanol-ZIF-8, 50.12% for water-based ZIF-8, and 65.36% for methanol-based ZIF-8 by 600 °C. In antibacterial studies, water-based ZIF-8 exhibited the largest zone of growth inhibition (17.30 ± 0.26 mm) against Escherichia coli compared to ethanol-based ZIF-8 (15.57 ± 0.32 mm) and methanol-based ZIF-8 (14.70 ± 0.20 mm). Pearson's correlation study revealed that zeta potential, crystallinity, and antibacterial activity are positively related. Furthermore, water-based ZIF-8, with a minimum inhibitory concentration of 50 μg/100 μL, confirmed evident cell membrane disruption. Molecular docking experiments revealed ZIF-8's significant binding affinity for the E. coli protein 5AZC, supporting its robust antibacterial activity.