Optimizing the antibacterial activity of an anionic metal-organic framework by post-synthetic cation exchange process

Developing new materials with antibacterial properties is a key objective in modern chemistry, aimed at addressing the growing challenges of antibacterial resistance, reducing reliance on traditional antibacterial substances, and minimizing environmental pollution. In this context, inorganic chemistry has made significant contributions through the development of porous materials and their integration with metal ions known for their antibacterial activity. In this study, an anionic metal–organic framework (MOF) was synthesized and subsequently modified through a cation-exchange process, in which the organic cation was replaced with antibacterial metal cations Cu 2+ , Zn 2+ , Ag + . In this regard, the anionic Zn-based MOF formulated as [HDMA] 2 [Zn 2 (BDC) 3 (DMA) 2 ].6DMF ( 1 ) (HDMA + = dimethylammonium, BDC 2− = benzene-1,4-dicarboxylate, DMA = dimethylamine, and DMF = N, N -dimethylformamide) underwent post-synthetic cation-exchange modification processes in the presence of Cu 2+ ( 2 ), Zn 2+ ( 3 ), and Ag + ( 4 ) solutions. The resulting MOFs were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FT-IR) spectroscopy, 1 H nuclear magnetic resonance ( 1 H NMR) spectroscopy, field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) mapping, zeta potential, and thermogravimetric (TG) analyses. Then the antibacterial activity of the samples was investigated against the Gram-positive and Gram-negative bacteria strains ( Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ), respectively) and compared with the antibacterial activity of the other studies. The antibacterial analysis demonstrated notable antibacterial activity across the samples, with a significant enhancement observed in those containing Ag + and Zn 2+ ions. Among the samples, sample 4 exhibited superior antibacterial performance compared to the others. Compound 1 , which contains zinc metal node that can act as an intrinsic antibacterial agent, was selected as the parent framework to enable a potential synergistic effect between the MOF structure and the incorporated antibacterial metal cations. The accessibility provided by the ion-exchange process offers a versatile strategy for enhancing antibacterial efficacy while potentially reducing bacterial resistance development and environmental impact.