Title screen

As an essential precursor, K2MnF6 plays an important role in the preparation of Mn4+-activated fluoride materials, but its deterioration in pure water hampers development of a green route. Herein, we report a simple and high-speed synthetic route to obtain an environmentally friendly water-soluble KHF2:Mn4+ luminous material by engineering the interstitial Mn4+ site, which is confirmed by combining with DFT, XRD Rietveld refinement data, solid-state NMR, Raman spectrum, and TG/DSC curves. Meanwhile, KHF2:Mn4+ has red emissions centered at ~602.2, 611.2, 615.6, 633.2, 637.2, and 650.0 nm, shows a zero-thermal-quenching characteristic and good quantum efficiency of 65%. KHF2:Mn4+, and as a green ion-exchange luminous material can be dissolved into pure water to produce anionic [MnF6]2- complexes for preparing Mn4+-activated fluoride phosphors such as K2GeF6, K2SiF6, K2TiF6, etc. This discovery reveals KHF2:Mn4+ is a potential candidate to substitute K2MnF6 to develop a green route for Mn4+-activated fluoride inorganic luminescent materials.