An Effective and Facile Method To Prepare Monofluorophosphates Overcoming the Common Difficulty of Loss of Fluorine and Serious Corrosion: 12 Examples and Their Characterizations and Properties

Abstract

Monofluorophosphate, being an important industry chemical, such as an additive in toothpaste, has been recently recognized as a new source of excellent deep-ultraviolet nonlinear optical materials with a desired large band gap and birefringence. To move this new material toward real application, an urgent demand is establishing an effective synthetic method owing to the easy loss of fluorine and serious corrosion of fluoride in the conventional methods. In this work, we establish a facile and green aqueous synthesis method overcoming the above-mentioned issues that can be generally applied to a wide range of monofluorophosphates by rational design either through acid–base neutralization or a metathesis reaction. To demonstrate such a method, we synthesized three types of representative monofluorophosphates that are crystallized with alkali metal cations (Na+, K+, Rb+, Cs+; 1–4), mixed cations (Li+NH4+, Na+NH4+, Li+K+, Na+K+; 5–8), and alkaline-earth metal cations (Mg2+, Ca2+, Sr2+, Ba2+; 9–12). Other than low cost and simple manipulation, the yield is pretty high (>80%). Thermal stabilities are also studied, nine of which are for the first time, revealing that [PO3F]2– usually stabilizes to 240–350 °C, whereas [PO3F]2– can stabilize to 650 °C in compounds without NH4+ or crystalline water.