When carbon nanotubes self-assembled in a 3D framework, it results in a sponge consisting of hollow, tiny, and strong carbon nanotube cylinders. They are elastic, lightweight, highly porous, and have chemical stability. They also possess high surface area, stable structure, and float on the water. They have great absorbance of solvents and oils from water and soil. It can absorb 180 times its weight, having water repellent capacity. It is widely used for environmental cleanup and as a catalyst.