A 3D Polyoxoniobate-based Framework Showing Performance in Dye Removal from Aqueous Solution

Abstract

A polyoxoniobate-based 3D framework [K[sub]8[/sub]H[sub]30[/sub]Nb[sub]6[/sub]O[sub]31[/sub]] (1) was prepared through a hydrothermal method and characterized by single crystal X-ray diffraction, Powder X-Ray Diffraction (PXRD), solid state UV-visible, and thermogravimetric analysis (TGA). Structure and properties of 1 were investigated by various computational methods. Quantum Theory of Atoms in Molecules (QTAIM) and NBO studies together with thermogravimetric analysis suggest the existence of strong interactions among potassium ion, Lindqvist hexaniobate, and water molecules. Hirshfeld surfaces around the Nb6O8-19 reveal that the Lindqvist ion acts as a $η$3 ligand for the alkali cations. One remarkable detail about the structure is the presence of an encaged potassium ion, surrounded by six water molecules and four potassium ions. The prepared polyoxoniobate (PONb) was tested in the removal of diazo dye pollutant in water. The result shows that 1 has good activity and stability during the dye removal process and can be recovered and reused at least for five cycles.