Hydrothermal synthesis and structural characterization of framework microporous mixed tin–zirconium silicates with the structure of umbite

A novel framework mixed tin–zirconium silicate, K2Sn0.25Zr0.75Si3O9·H2O (1), was synthesized under mild hydrothermal conditions. The unit cell is orthorhombic, a=10.260(2) Å, b=13.272(2) Å, c=7.174(1) Å, space group P212121, Z=4. Isotypic with the mineral umbite, the structural formula may be written as K2(Sn,Zr){uB,1∞1}[3Si3O9]. In a topotactical process, the K+ ions in compound 1 were replaced by Na+ ions, thus obtaining compound 2: Na2Sn0.25Zr0.75Si3O9·H2O (2), a=10.500(1) Å, b=13.354(2) Å, c=7.2731(9) Å.