Cation- and Anion-Substituted Potassium Manganese Phosphate, KMnP₃ O₉ : 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 (KMnP₃ O₉ ) (hereafter KMPO), was prepared by solid state method. Cations (Ag⁺ and Cu²⁺ ) and anion (N^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 KCoP₃ O₉ . The nitrogen content in N^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 Mn²⁺ 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^3- -substituted KMPO, was examined against the degradation of methylene blue and methyl violet at ambient conditions.