Na3Hx(H2PO4)x((GEO)4(GeO4)3).4H2O: A Rhombohedrically-Distorted GermaniumPharmacosiderite Analog with Anion/Cation Exchange Capabilities. (Reannouncement with New Availability Information)

摘要

A rhombohedrally distorted germanium pharmcosiderite analog, with thestoichiometry of Na3H(x)(H2PO4) (x)((GeO)4(GeO4)3).4H2O, X = 1.38, has been synthesized under mild conditions. As synthesized, this material contains both sodium cations and hydrogen phosphate anions as included species. Both monovalent/divalent cations and a variety of anions are easily exchanged in and out of the framework under aqueous conditions atroom temperature. Depending on the ions incorporated, the crystal structure can be transformed to the cubic system space group P43m (No. 215) and then back to the rhombohedral system. It appears that the incorporation of a sodium cation and any cation will induce the rhombohedral distortion. Rietveld refinement of room-temperature powder X-ray and time-of-flight neutron powder data confirmed the space group R3m (No. 160) with a = 7.7121 (4) A and alpha = 89.04 (3) deg, final R =3.32% and Rw = 3.93% (chi squared = 5.055) for 63 variables and 10 693 observations. Crystallographic data for two ion-exchanged cubic frameworks are included along with data for a synthesized cubic K3H(GeO)4(GeO4)3.4H2OK/Ge framework. Further analytical studies, such as31P MAS NMR and FTM, were used to confirm the presence of absence of cation and/or anion exchange for all analogs studied.