Synergistic engineering of NiCo- layered double hydroxide/ZIF-8 for constructing a flame-retardant and superhydrophobic sponge toward safe oil-water separation

Polyurethane (PU) sponges are promising for oil-water separation, but their high flammability poses serious safety risks. To address this challenge, a multifunctional composite sponge was prepared by decorating a PU scaffold with a synergistic coating of polydimethylsiloxane (PDMS), NiCo-layered double hydroxide (LDH), and ZIF-8. This NiCo-LDH/ZIF-8@PDMS@PU composite sponge integrates superhydrophobicity, high oil-adsorption capacity, and intrinsic flame retardancy. The composite sponge exhibits a water contact angle of 153.4° and achieves self-extinguishing behavior, increasing the burning time from 5 s (pristine PU) to 16 s while eliminating melt dripping and reducing toxic fume emission. It shows high saturation adsorption capacity (26.6-82.9 g/g) for various oils and organics, and separation efficiency exceeding 99%, which remains above 98.5% after 20 adsorption-extrusion cycles. Furthermore, the composite sponge maintains its superhydrophobicity and separation performance after exposure to extreme pH, saline, and mechanical agitation conditions, demonstrating excellent environmental stability. This work provides a durable and safe material solution for oil-spill remediation, highlighting the great potential of multi-component synergistic design in developing advanced separation materials.