K4Nb6O17·4.5H2O: A novel dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III)

A well crystalline K4Nb6O17·4.5H2O with a wide layer spacing possesses an excellent disposal performance for chromium species of Cr(VI) and Cr(III) as well as the superior recyclability due to its high stability and convenient regeneration process.