A rare potassium-rich zirconium fluorophosphonate with high Eu³⁺ adsorption capacities from acidic solutions

A novel 3D potassium-containing zirconium fluorophosphonate K₂Zr[CH₂(PO₃)₂]F₂ (SZ-8) was successfully synthesized as single crystals via a solvothermal method using a mixture of nitric acid and potassium nitrate as mineralizers. SZ-8 can adsorb 110.6 and 57 mg g^-1 of Eu³⁺ in pH 2 and pH 1 solutions respectively, highlighting its potential remediation for radionuclides with high charges. SZ-8 not only possesses superior Eu³⁺ removal capacity under strongly acidic conditions, but also provides a universal synthesis strategy for crystalline zirconium phosphonates with inorganic counterions.