A superhydrophobic, photothermal, and flame-retardant sponge modified with hydrophobic mesoporous silica for rapid oil adsorption and separation

Superhydrophobic sponge materials offer a promising solution for treating oily wastewater. To address the challenges of hydrophobic modifier leaching and process complexity, this study developed a composite sponge by immobilizing hydrophobically modified mesoporous silica nanoparticles (H-DMNH) onto a polydopamine (PDA)-modified melamine sponge (MS) framework. Hydrophobic long-chain siloxanes were grafted onto the mesoporous silica nanoparticles (DMNH) via hydrothermal synthesis, and the resulting H-DMNH was firmly anchored onto the PDA coated MS sponge through electrostatic interactions, hydrogen bonding, and hydrophobic interactions. The obtained H-DMNH/PDA@MS sponge exhibits integrated and durable superhydrophobicity with a water contact angle (WCA) of 154°, antifouling properties, high oil absorption capacity (36.2–118 g/g), efficient separation of oil/water mixtures and emulsions (>97%), and good recyclability. Under simulated solar irradiation, the H-DMNH/PDA@MS sponge surface temperature rapidly rises to 65 °C within 1 min, achieving a photothermal conversion ability of 88.3%, thereby promoting adsorption through reducing oil viscosity. Furthermore, the H-DMNH/PDA@MS sponge shows certain flame-retardant characteristics (loss rate is 25.6%), which substantially enhance operational safety in flammable environments. With this multifunctional attribute, the H-DMNH/PDA@MS sponge emerges as a robust and sustainable material for practical oil-water separation applications.