Magnetically driven superhydrophobic silica sponge decorated with hierarchical cobalt nanoparticles for selective oil absorption and oil/water separation

Three-dimensional superhydrophobic/superoleophilic materials (3D-HOMs) with remote controllability are highly desirable for water remediation. Herein, a new monolithic silica sponge decorated with hierarchical cobalt (Co) nanoparticles that fulfils almost all major requirements and applications for water remediation was fabricated by self-assembly electrospinning, controlled particle precipitation, and subsequent surface coating. Attributing to the continuous silica fibers and the hierarchical Co microstructures, the modified silica sponge (MSS) possesses excellent superhydrophobicity and oil selectivity, low bulk density (49 mg/cm³), high surface area (8.7 m²/g) and absorption capacity (45–91-fold weight gain), ultrahigh thermal resistance (tolerance to liquid nitrogen and combustion), flexibility, deformability, durability, and remote controllability through magnetic field manipulation. Moreover, simply compacting MSS can easily enhance its separation efficiency by bringing the interior structures to the contacting interfaces, which solves the performance deterioration issue over time for most 3D-HOMs. With all of these satisfactory properties, MSSs can be used as both durable magnetic superabsorbers and efficient oil/water separation filters with a long life span.