An alkali rare-earth phosphate K2RbSc(PO4)2 was successfully obtained as a derivative of glaserite-type K3Na(SO4)2 by co-substitution of K(1)O12 → RbO12, K(2)O10 → KO7, NaO6 → ScO6 and SO4 → PO4, while maintaining the original anionic framework. K2RbSc(PO4)2 exhibits a layered [Sc(PO4)2]∞ framework built from ScO6 octahedra and PO4 tetrahedra, with K and Rb residing in the interlayers. Its isostructural lanthanide analogues K2RbEr(PO4)2 and K2RbLu(PO4)2, inspired by an elemental substitution strategy, were also prepared by a high-temperature solid state reaction. The successful substitution indicates that the skeleton of K2RbSc(PO4)2 is stable with high structural tolerance, which can provide a possibility for substitution of resident ions to obtain diverse structural types and applications.