Superhydrophobic ZIF8/PDMS-coated polyurethane nanocomposite sponge: Synthesis, characterization and evaluation of organic pollutants continuous separation

Oil spills have caused significant environmental problems, placing the requirement of efficient and low-cost materials for the decontamination and cleanup. In attempts to answer for this requirement, in this work superhydrophobic nanocomposite sponges were developed, based on readily available and low-cost polyurethane (PU) sponges due to robustness and macro-porous structure, which were dip coated by the zeolitic imidazolate framework (ZIF8) metalorganic framework as low density crystal and tunable microporous structure and polydimethyl siloxane (PDMS) to increase the hydrophobicity. The obtained composite sponges presented a nice porous structure, the surface of which was uniformly covered with the crystals of ZIF8 and PDMS. Therefore, the superhydrophobicity was obtained to show the water contact angle as high as 156º, which was prone to be wet by oils. The high-water contact angle was preserved even in the acidic and basic environment due to the physico-chemical modification of the PU surface that provided improved chemical resistance and increased hydrophobicity. Accordingly, the nanocomposite sponges absorbed low water amount (0.5 g/g) and high oil amount (58 g/g) and presented an excellent oil/water separation performance. The synergistically combined materials along with the excellent surface and porous properties were accounted for the performance attained.