Extremely efficient and recyclable absorbents for oily pollutants enabled by ultrathin-layered functionalization.

Oils and organic solvents that leak into water bodies must be promptly removed to avoid ecological disasters, for example, by selective absorption using oleophilic absorbents. However, it remains a challenge for the low-cost synthesis of efficient and recyclable absorbents for oily pollutants. By surface functionalization to inexpensive polyurethane (PU) foams, we synthesize oil absorbents exhibiting the highest absorption capacity and the best recyclability among all polymeric absorbents. The synthesis is enabled by atomic layer deposition of ∼5 nm-thick Al2O3 transition layer onto the skeleton surface of PU foams, followed by coupling a single-molecule layer of silanes to the Al2O3 layer. The sub-10 nm functionalization layer provides the PU foam an outstanding water-repelling and oil-absorbing functionality without compromising its high porosity and elasticity. The functionalized foam is able to quickly absorb oily pollutants spread on water surfaces or precipitated in water with a capacity more than 100 times its own weight. This ultrathin-layer-functionalization method is also applicable to renewable porous biomaterials, providing a sustainable solution for oil spills. Moreover, we propose devices than can continuously operate to efficiently collect oil spills from water surfaces based on the functionalized PU foam developed in this work.