Three fluorooxoborates, K0.42Rb2.58B3O3F6 and M3B2PO5F4 (M = K, Cs), were designed and synthesized under the open system. One of the common features is that the title compounds consist of six membered oxofluoride anions. The oxofluoride anions [B3O3F6](3-) and [B2PO,F-4](3-) display structures similar to the boroxine [B3O3F6](3-). Anionic group substitution using the [BO2F2](3-) and [PO4](3-) units can improve the optical property of the [B3O6](3-) anion and help to generate a wide transmittance window.