Design, Synthesis, and Characterization of Polyoxotungstate-Decorated Ionic Liquid–Based Hybrid Material, [BmIm]₄[SiW₁₂O₄₀] toward Rapid Adsorption of Dye and Antibacterial Activities

A multifunctional polyoxometalate-ionic liquid (POM-IL)-based hybrid material comprising silicotungstic acid, [BmIm]₄[SiW₁₂O₄₀], has been synthesized and demonstrated its efficiency toward methylene blue removal and as an antibacterial agent. Single-crystal XRD analysis confirms that the material crystallizes in monoclinic symmetry (SG: <i>Pn</i>), with lattice parameters <i>a</i> = 13.1396(5) Å, <i>b</i> = 16.9655(8) Å, <i>c</i> = 14.3493(7) Å, and <i>Z</i> = 2. The structure comprises a single polyanionic [SiW₁₂O₄₀]^4- moiety surrounded by four cationic [BmIm]⁺ units of two different conformations, which supported DFT and Hirshfeld surface analysis. The material shows excellent removal efficiency for methylene blue, with a maximum adsorption capacity of 92.47 mg/g and 83.05% reusability after five cycles. On the contrary, FTIR and ζ-potential analyses confirm that electrostatic interactions are the predominant factors governing the adsorption process. The material also acts as a superior antibacterial agent against the opportunistic pathogens <i>Pseudomonas aeruginosa</i>, <i>Klebsiella pneumoniae</i>, and <i>Escherichia coli</i> with a MIC of 500-700 μg/mL. However, a comparative assessment showed that the material was more effective against <i>P. aeruginosa</i> compared to the other two pathogens. PXRD analysis confirms the phase purity, and FESEM and TEM analyses exhibit block-shaped morphology with particle sizes ∼2-3 μm.