TiO2, a material which usually does not absorb visible light, is made in a highly porous form. Tungsten (W) and nitrogen were incorporated in the material using some simple approaches to result in TiO2 that absorbs in the visible region! Furthermore this material was used for purifying water, using the sunlight they were capable of harvesting, owing to the fact that they could now absorb in the visible!

Ref: Solid State Sciences Volume 54, April 2016, Pages 49-53