Modulated Optoelectronic Properties of MOF/CNF Bionanocomposite Films for Bacterial Growth Control under Visible Light

The present work reports an experimental and theoretical investigation of tuning the optoelectronic properties of MIL-125-NH₂ nanoparticles by grafting aromatic molecules. The postsynthetic modification of the MOF MIL-125-NH₂ with 3,4-dihydroxybenzaldehyde (DBA) resulted in a 23% reduction in the bandgap energy, from 2.71 to 2.08 eV, while increasing the absorbance throughout the visible region of the spectrum, which could be attributed to stabilization due to enol-imine/keto-enamine tautomerism, as supported by DFT theoretical calculations. Pristine and grafted MOFs were assembled into cellulose nanofibers (CNF) for the preparation of functional CNF-based bionanocomposites. The mechanical properties of the films improved, with Young's modulus increasing from 1.3 GPa in CNF to 7.5 GPa in the film with 20% MOF loading. The potential of the developed materials for photocatalytic antimicrobial therapy was evaluated against <i>Staphylococcus aureus</i> (<i>S. aureus</i>). In vitro tests showed that both bionanocomposite films with pristine and DBA-modified MOF remarkably reduced bacterial growth due to the photocatalytic action of the MOF under visible light. The inhibition values were around 58% and 72%, respectively, while minimal inhibition was observed under dark conditions. These initial results support the potential use of the developed bionanocomposite films as wound dressings.