Nonflammable, robust and recyclable hydrophobic zeolitic imidazolate frameworks/sponge with high oil absorption capacity for efficient oil/water separation

Developing robust sponge-based materials with high oil capacity and excellent flame resistance for oil spill cleanup is significant. Herein, a highly hydrophobic composite sponge material for oil-water separation, containing a melamine-formaldehyde (MF) sponge substrate and zeolitic imidazolate framework-8 (ZIF-8) coating was fabricated through the simple amino-assisted in-situ growth of ZIF-8 onto the strut surface of MF sponge. The successful integration of MF sponge and ZIF-8 nanoparticles in one composite material was confirmed by scanning electron microscopy, X-ray diffraction and nitrogen sorption. The synergistic effect of the MF substrate and ZIF-8 coating significantly improved its flame resistance. Combining the advantage of the MF substrate and the hydrophobic ZIF-8 nanocrystals, the ZIF-8/MF composite sponge showed high porosity and good hydrophobicity with a water contact angle of 130°. A high adsorption capacity towards various oils was achieved in the range of 76–164 g g −1 . Besides, the ZIF-8/MF composite sponge exhibited excellent separation performance for light oil/heavy oil-water mixtures via adsorption and/or gravity-driven separation. In addition, owing to its compressibility and mechanical stability, the ZIF-8/MF composite sponge could be easily regenerated by a simple squeezing method and showed excellent recyclability for the oil adsorption. These features make the ZIF-8/MF composite sponge promising for highly efficient oil-water separation. ● Hydrophobic ZIF-8/melamine-formaldehyde (ZIF-8/MF) composite was designed via in-situ growth. ● ZIF-8/MF showed selective absorption for numerous oils with high oil capacity. ● The highly efficient separation of multiple type oil-water mixtures was achieved. ● ZIF-8/MF exhibited good recyclability with promising flame resistance.