Advanced Nb-doped ZnO/ZIF-8 nanocomposite: a synergistic smart strategy for catalytic functionality in preparation of spiro[indene-2,2'-naphthalene]-4-carbonitriles and antibiotic resistance.

In recent decades, the increasing prevalence of antibacterial resistance and the growing global demand for efficient, sustainable catalytic systems have emerged as critical frontiers in pharmaceutical and materials science. This pressing necessity has prompted the development of multifunctional nanocomposites with integrated therapeutic and synthetic capabilities. In this study, a novel Nb-doped ZnO/ZIF-8 hybrid composite was designed and prepared as a synergistic, high-performance dual-purpose nanostructure for broad-spectrum antibacterial and highly efficient catalytic functionality. Structural engineering via niobium doping significantly refined the composite topology, reducing the average crystallite size to 25 nm and optimizing the pore diameter to 9.68 nm (S BET = 87.35 m2 g-1), thereby maximizing the accessible active sites. Benefiting from enhanced electronic charge separation and the resulting improvement in interfacial electron transfer, the designed composite exhibited robust antibacterial activity against both Gram-negative and Gram-positive bacteria, particularly Staphylococcus aureus and Enterococcus faecalis, with inhibition zones of 18 and 21 mm, respectively, and a 5-log reduction in viability within 24 h. These empirical findings suggest a potent oxidative-stress-inducing mechanism suitable for combating resistant clinical pathogens. Furthermore, the hybrid composite demonstrated exceptional utility as an outstanding heterogeneous catalyst for the preparation of medicinal substituted spiro[indene-2,2'-naphthalene]-4-carbonitrile derivatives in an ethanol medium, achieving excellent yields (up to 98%) within 20 minutes and retaining high catalytic functionality over five consecutive runs without significant leaching. This study highlights the potential of Nb-doped ZnO/ZIF-8 as a robust dual-purpose composite for antimicrobial applications and sustainable catalysis in green organic synthesis, offering a scalable, environmentally benign paradigm for addressing contemporary biomedical and catalytic challenges.