Cation- and Anion-Substituted Potassium Manganese Phosphate, KMnP sub(3)O sub(9): Luminescence and Photocatalytic Studies

Phosphates as multifunctional materials were of vital importance in the environmental and energy fields. In the present work, a new cyclophosphate, potassium manganese phosphate (KMnP sub(3)O sub(9)) (hereafter KMPO), was prepared by solid state method. Cations (Ag super(+) and Cu super(2+)) and anion (N super(3-)) were substituted into KMPO lattice via ion-exchange and solid state methods, respectively. The as-prepared materials were characterized by powder X-ray diffraction, SEM-EDS and UV-visible diffuse reflectance spectra. Rietveld refinement was carried out for parent material. All the prepared materials were found to crystallize in the hexagonal lattice and isomorphous with KCoP sub(3)O sub(9). The nitrogen content in N super(3-)-substituted KMPO was estimated by EDS and O-N-H analysis. The bandgap energy of the cation- and anion-substituted samples was lower compared to that of pristine KMPO. Gouy method was employed to determine the magnetic susceptibility of KMPO. The photoluminescence property of Mn super(2+) in all the samples was studied, and the color coordinates were calculated using CIE 1931 chromaticity. The photocatalytic activity of visible light active material, N super(3-)-substituted KMPO, was examined against the degradation of methylene blue and methyl violet at ambient conditions. The framework structure of KMnP sub(3)O sub(9) is built from P sub(3)O sub(9) super(3-) anions sharing corners or edges with MnO sub(6) polyhedra. Potassium ions are located in P sub(3)O sub(9) tunnels and surrounded by six oxygen atoms.