Superhydrophobic PDMS/MOF-74@PU sponge with photothermal property for efficient oil/water separation

The frequent oil leakage accidents cause huge loss of natural resources and serious damage to the ecosystem. Although all kinds of modified sponges have been invented to deal with the offshore oil spills, it is difficult to separate high viscosity crude oil and water-in-oil emulsions. To address these challenges, a modified polyurethane (PU) sponge (PDMS/MOF-74@PU) coated by polydimethylsiloxane (PDMS) with ultra-low surface energy after growing spindle-shaped metal–organic framework structure (MOF-74) on the PU sponge surface was prepared. With the advantages of super-hydrophobic and high porosity, the prepared sponge can selectively and effectively absorb various oils from oil/water mixtures and it has good oil adsorption capacity (18–55 g/g). Meanwhile, the black MOF-74 endows the PDMS/MOF-74@PU photothermal properties for the separation of high viscosity crude oil under the light conditions. As well as, the prepared sponge shows excellent separation performance for the water-in-oil emulsions, the amount of water in the oil could reduce to less than 20 ppm and the separation efficiency could reach as high as 99.9 % after separation. In addition, we used molecular dynamics to verify the mechanism by which PDMS coatings change the surface wettability of materials. With the excellent mechanical property, chemical stability, and thermal stability in various harsh environments, the PDMS/MOF-74@PU have a broad application prospect in the treatment of offshore oil spills.