Synthesis and Characterization of Zirconogermanates

Six new zirconogermanates have been prepared under hydrothermal conditions using amines as bases. There are four new structure types (ASU-n) with a common motif of ZrGe5. ASU-23 is a layered structure: ZrGe3O8(OH)F·[C10H26N4]·H2O, space group P21/n, a = 6.7957(8) Å, b = 12.700(1) Å, c = 24.293(3) Å, β = 97.936(2)°, V = 2076.4(4) Å3. ASU-24 is a pillared layered structure: Zr3Ge6O18(OH2,F)4F2·[C6H18N2]·[C6H17N2]2·2H2O, space group P21/n, a = 7.4249(3) Å, b = 25.198(1) Å, c = 11.3483(5) Å, β = 90.995(1)°, V = 2122.9(2) Å3. This material has the lowest framework density (FD) of any oxide material that we are aware of (FD = 8.48 metal atoms/nm3). Two other materials form three-dimensional open-frameworks, ASU-25: ZrGe3O9·[C3H12N2], space group P1121/a, a = 13.1994(4) Å, b = 7.6828(2) Å, c = 11.2373(3) Å, γ = 91.233(3)°, V = 1139.29(5) Å3. The other is ASU-26: ZrGe3O9·[C2H10N2], space group Pn, a = 13.7611(3) Å, b = 7.7294(2) Å, c = 11.2331(3) Å, β = 104.793(1)°, V = 1155.21(4) Å3. ASU-25 is related to the mineral umbite K2ZrSi3O9·H2O. The germanium equivalent has been prepared through the inorganic route: K2ZrGe3O9·H2O, space group P212121, a = 13.6432(6) Å, b = 7.4256(3) Å, c = 10.3973(4) Å, V = 1053.33(8) Å3. The structural relationships between ASU-25 and its inorganic counterpart are described. The thermal decomposition of the germanium umbite generated the cyclic trigermanate K2ZrGe3O9, analogue of the mineral wadeite, crystallizing in the orthorhombic system, a = 7.076 Å, b = 12.123 Å, c = 10.451 Å, V = 904.5 Å3.