Explanation:
The bulk of the sponge in the video is made up of a material called polyurethane. This polymer has the convenient property that it can be easily be used to create very porous foams. Now to turn the foam into a sponge capable of soaking up oil, researchers did two additional steps shown in this diagram:
1. First, they coated the surface of the foam with aluminum oxide (Al2O3). To achieve this they used a process called sequential infiltration synthesis.
2. They then used a silane agent to turn the aluminum oxide oleophilic, or attracted to oil particles.
The net result is that they got a material with large surface area, where the surface is attracted to oil. As a result, if you take a sponge of this material and put it in a water/oil mixture, the sponge can quickly soak up the oil. The hope is that materials like this can be cheaply manufactured on a mass scale to help clean up oil spills whenever they happen.