Biomimetic sponge for photocatalytic water purification

We report the design of a biomimetic sponge for photocatalytic purification of water. Our focus is on the hierarchical structural features that enable pollution remediation under natural conditions of sunlight irradiation and no stirring. The biomimetic sponge is created from the designed self-assembly of photoactive TiO2 nanoparticles with a natural organic molecule cyclodextrin. These materials assemble into a network of microscale fibers with lengths extending beyond millimeters. The highly interconnected nature of these fiber networks provides both the mechanical stability and large pore structure needed for water purification applications. We demonstrate that this biomimetic structure is capable of degrading a common organic pollutant and find that the percentage of TiO2 in the network structure controls the degree of pollutant degradation. In addition, the cyclodextrin in the network is seen to enhance photocatalysis through trapping of the pollutant molecules near the active titania surface. Finally, we discuss the next steps needed to mimic more faithfully the operation of a real biological sponge.