Coating polyurethane sponge with Dy-MOF for efficient oil–water separation in complex environments

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Leakage of industrial oil and organic solvents seriously harms environment and ecology yet demanding highly efficient and durable materials for oil–water separations. In this work, ultra-light and highly flexible polyurethane (PU) sponges were engineered to 3D oil–water separators by coating the dysprosium metal organic framework (Dy-MOF) onto the surfaces of the PU frames. Through a facile impregnation, the Dy-MOF was attached to the full frames of the sponges. Consequently, liquid contact surfaces were extended from these on top layers to the whole rack. Superhydrophobicity with water contact angles up to 152.08° and lipophilicity enable continuous separations of dichloromethane from water through the resulted Dy-MOF@PU sponges in a continuous mode. The modified sponges own high gravimetric absorption capacities for oil and organic solvents, and high resistances to temperature variations, corrosive solutions, and mechanical abrasions, thanks to the well-connected and stable superhydrophobic/supportive interfaces. An efficient separation was successfully piloted for oily wastewater consisting of water-in-oil emulsions stabilized by surfactants, demonstrating the potential of practical water treatment of Dy-MOF@PU in complex environments. Mechanism leading to superior oil–water separation capability was studied and inferred as the combined effects of the physical and chemical properties arisen from the stable Dy-MOF and flexible but porous matrix.