Superhydrophobic sponge decorated with hydrophobic MOF-5 nanocoating for efficient oil-water separation and antibacterial applications

Increased discharge of industrial oily effluent threatens the environment and human health; thus, researchers are developing effective methods to separate oil from water. Recently, superhydrophobic surfaces with oil-water separation properties have received attention. In this study, we proposed a simple method to fabricate superhydrophobic/superoleophilic sponges decorated with zinc (Zn)-based metal-organic frameworks (MOF-5) with oil-water separation and antibacterial properties. The synthesized superhydrophilic MOF-5 nanoparticles were hydrophobized using low surface energy 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) material. Finally, a simple dip-coating process was performed to prepare superhydrophobic sponge after altering hydrophobic MOF-5 (H-MOF-5) with polydimethylsiloxane (PDMS). The synergistic effect between the H-MOF-5 and low surface energy PDMS resulted in superhydrophobicity. The fabricated sponge showed water repellency with a high water contact angle (WCA) of 156° and a sliding angle (SA) of 6°. In addition, it exhibited extraordinary oil-water separation and antibacterial properties. Superhydrophobic sponges can be used to remove light or heavy oil-water mixtures using absorption under stirring and a gravity-driven separation approach, respectively. Continuous separation of various types of oil/organic solvent-water mixtures was demonstrated using a vacuum-assisted method with separation efficiency >98%. The sponge displayed exceptional reusability, maintaining a high separation efficiency of over 95% and retaining WCA at 153° after 10 cycles. The antibacterial property of the copper substrate modified with superhydrophobic PDMS@H-MOF-5 coating was investigated against Staphylococcus aureus bacteria using the inhibition zone method. In comparison to an uncoated copper surface, the superhydrophobic surface demonstrated significant bacterial resistance efficacy with a 30 mm zone of inhibition. The proposed approach offers new opportunities for preparing a superhydrophobic sponge with hydrophobic MOF-5 nanoparticles for various applications, including oil-spill cleaning and organic pollutant removal on water surfaces.