Zirconium phosphate structure

Kumar, C.V. and Choudhari A. (2000) Proteins immobilized at the galleries of layered alpha-zirconium phosphate structure and activity studies. Journal of the American Chemical Society, 122, 830-837. 

In contrast to the conventional approach whereby various organic groups are subsequently bound to a previously prepared surface, we have been synthesizing a broad series of anchored, layered-structure solids by precipitating the pre-derived phosphonate salts with tetravalent metal ions. The two-dimensional backbone has the zirconium phosphate structure however, substituted for hydroxylic groups are the desired organics, oriented away from the basal surfaces in a bilayered fashion in the interlayer region. 

The matching between the guest molecules and the host structure was also considered to explain the in situ polymerization of e-aminocaproic acid in zirconium phosphate [29]. The schematic representation of the arrangement... 

X-Ray diffraction studies have identified a distorted octahedral environment about zirconium in KZr2(P04)3, and the structures of zirconium phosphates have been discussed in terms of their utility as chemical sieves.Some preparative and structural aspects of the normal sulphates of zirconium and hafnium have been reviewed and X-ray studies have shown that the sulphates Zr20(S04)3,5H20 and Hf20(S04)3,5H20 are isostructural and are more accurately represented as M2(OH)2(S04)3,4H20. Other studies of zirconates and hafnates and related mixed oxide systems are summarized in Table 2. 

Sheetz, B. E., Agrawal, D. K., Breval, E. Roy, R. 1994. Sodium zirconium phosphate (NZP) as a host structure for nuclear waste immobilization A review. Waste Management, 14, 489-505. 

Figure 3 Partial schematic structure of ot-zirconium phosphate lamallae and its preparation.

Zinc [37], manganese [38], molybdenum [34], and vanadium [40,41] also form lamellar structures. For example, molybdenyl phenylphosphonate forms a linear structure with double chains in which the molybdenyl oxygens of the adjacent chains point toward each other and the phenyl groups are on the outside [42], As is the case with zirconium phosphate and phosphonate, the layered nature of the above metal phosphonates is similar to that of the respective phosphates. Among these, vanadium phosphonates have generated greater interest in view of their importance as industrial catalysts. 

Figure 30 Schematic representation of the polar orientation of the dyes in the multilayers of zirconium phosphate-phosphonate interlayers. This scheme is based on the known structures of Zr(H0P03)2 and related organic Zr phosphonate salts. (From Ref. 65a. Copyright 1991 The American Association for the Advancement of Science.)...

Figure 3. Three basic strategies for the incorporation of multiply bonded metal-metal guest species into vanadyl and zirconium phosphate host layers, (a) The direct intercalation of solvated M—— M cores into the native layered phosphate host structure, (b) Incorporation of M—— M complexes with ancillary ligands containing a Lewis basic site, (c) Coordination of M—— M cores with ligands provided from modified phosphate layers.

The ability to modify the backbones of LMP structures with phosphonates allows for wide flexibility in the design of new materials containing photoactive binuclear metal cores. The goal of our initial studies has been to demonstrate that a ligating functionality within the gallery is accessible for reaction with a bimetallic core. To demonstrate these initial objectives, we have chosen to study zirconium phosphate modified with alkyl carboxylate, which is a good ligand of bimetallic cores. 

It is known that non-aqueous synthesis has been effectively applied in the preparation of various metal phosphates, including amine-containing aluminum, gallium, indium, zinc and cobalt phosphates with three-dimensional open-framework structures [17-24]. Moreover, phosphates with a layered or chain structure can been crystallized from non-aqueous media [25, 26]. Since the fluoride ions mineralizer was introduced into the synthesis of zirconium phosphates, several zirconium phosphate fluorides with novel structures have also been developed. 

Up to now, only two one-dimensional zirconium phosphates have been reported. One is [enH2][Zr(HP04)3] [16], and the other is zirconium phosphate fluoride [enH2]i.5[Zr(P04)(HP04)F2] [13] with double-stranded chains. The simple models of one-dimensional chain inorganic polymers are shown schematically in Figure 2. ZrPO-3 has a chain- structure similar to the one-dimensional aluminum phosphate, [A1P208H]2 [29]. 

Figure 2. One-dimensional chain structures for zirconium phosphates.

Figure 12 idealized structure of a-zirconium phosphate (a-ZrP) showing one of the zeolitic cavities created by the arrangement of the layers. (From G. Alberti, in Study Week on Membranes (R. Passino, ed.), Pontificiae Acad. Sci. Scripta, Varia, Rome, p. 629, 1976. With permission.)... 

The a-zirconium phosphate has a layered structure in which each layer consists of a plane of zirconium atoms coordinated octahedrally to oxygen. The free space in the sides of the layered structure is large enough to allow a spherical ion of 0.263 nm diameter to diffuse the cavity without any obstruction and is accessible to Li, Na" and K" " [139]. However, the size of the window is smaller than the ionic spheres of Rb (0.296 nm) and Cs (0.338 nm) and an ion sieve effect is encountered with these ions. 

The pyrophosphate of uranium(IV) has been obtained and the structure determined to belong to the ZrP207-type structure. " Octahedral sites in the zirconium phosphates can accommodate U, as exemplified by the Na dizirconium tris(phosphate) structural family ([NZP]). An end member in this study was monoclinic KU2Zr(P04)3, which contains nine-coordinate Compounds of the general formula MU2(P04)3 have been reported for... 

Ri/M 2(P04)3. a double americium zirconium phosphate Ami/3Zr2(P04)3 (M = Zr) was synthesized and characterized by X-ray diffraction methods [74,75], This phosphate belongs to the NZP structure type. The NH4H2PO4 solution was added to the starting solution of americium nitrate and ZrOCU thermal treatment of the precipitates was carried out stage-by-stage up to 800°C. 

---