Two novel open-framework zinc phosphates: (CH3NH3)Zn4(PO4)3 and (CH3NH3)2Zn5(PO4)4

Abstract

Two methylammonium containing zinc phosphates, (CH₃NH₃)Zn₄(PO₄)₃ and (CH₃NH₃)₂Zn₅(PO₄)₄, have been synthesized hydrothermally from a mixture of zinc chloride, phosphoric acid and methylammonium hydroxide. (CH₃NH₃)Zn₄(PO₄)₃ crystallizes in space group Pbca, with a = 14.6797(6) Å, b = 10.1204(4) Å, c = 16.6015(7) Å and (CH₃NH₃)₂Zn₅(PO₄)₄ crystallizes in space group P2₁2₁2₁, with a = 7.265(2) Å, b = 13.432(4) Å, c = 18.078(5) Å. They have open framework structures formed by corner sharing of PO₄ and ZnO₄ tetrahedra with some of the oxygen atoms three-fold coordinated. One-dimensional tunnels are formed in both compounds, with the methylammonium template residing in the tunnels. There are extensive Zn–O–Zn chains in (CH₃NH₃)Zn₄(PO₄)₃; however, in (CH₃NH₃)₂Zn₅(PO₄)₄ the Zn–O–Zn bonding is restricted to isolated Zn₄O₁₂ units.