Vanadium open framework

Fig. 15. Projection of the structures of the vanadium phosphonate MIL-2 (left) and of a lanthanide glutarate (right), two hybrid inorganic-organic open frameworks.

All of the above compounds are oxides. The application of the fluorine route already described for AlPOs and GaPOs has shown that it is also possible to obtain open framework structures with fluoride in the VPOs. This led to the discovery by Riou and Ferey [72] of the first open-framework fluorovanado(V)phosphate, ULM-7 or (H3N(CH2-CH2)NH3)[(V 02)2(P04)F], in which the building units are V2P trimers. Vanadium exhibits both octahedral and square pyramidal coordination, and fluoride ion is shared between them. The three-dimensional network generated by comer-sharing of these trimers, exhibits 10-membered rings occupied by diprotonated amines. 

Vanadium Phosphates with Extra-large Pores and Chiral Open Frameworks... 

Polyoxometalates and their derivatives can be amalgamated with a variety of ligands. An impressive array of vanadium-oxide-phosphate based materials with new electronic and structural properties has been prepared by combining the tetrahedral PO4 ligand with oxovanadate moieties. Some of these materials have open-framework containing very large cavities and channels similar to those observed in conventional aluminosilicate-based zeolites . 

Although the structural chemistry of molybdenum and vanadium phosphates is very diverse these compounds seem to be prototypes for open framework transition and main group metal phosphates. Recent results have shown that zeolite-like compounds like zinc/cobalt phosphates [731, indium phosphates [74], nickel/aluminum phosphates [75], cobalt/boron phosphates [76], manganese and cobalt phosphonates with giant 44-membered rings forming ellipsoidal cavities [77] can be synthesized. All these examples show that the diverse chemistry of octahedral-tetrahedral framework structures is a vast field where... 

Open-Framework Solids of the Vanadium Oxide Phosphate System 139... 

OPEN-FRAMEWORK SOLIDS OF THE VANADIUM OXIDE-PHOSPHATE SYSTEM... 

P.Y. Zavahj, M.S. Whittingham, Stractural chemistry of vanadium oxides with open frameworks. Acta CrystaUogr. Sect. B Struct. Sci. 55(5), 627-663 (1999)... 

Riou, D., Roubeau, O., and Ferey, G. Composite microporous compounds. Rart I Synthesis and structure determination of two new vanadium alkyldiphosphonates (MIL-2 and MlL-3) with three-dimensional open frameworks. MicroporMesoporMat 23,23-31(1998). 

More recently, lithium vanadium phosphates (LisV2-(P04)s and Li3FeV(P04)3, with open NASICON framework structures, have also been studied. Reversible electrochemical lithium deintercalation/re-intercalation at a higher potential (in comparison to the couples seen for the oxides) of between 3... 

Using this approach leads to replace phosphates by other chelating agents. The first attempts concerned phosphonates and were developed by Alberti and Clearfield ([76] and Refs therein) in the early seventies. These authors showed that phosphonates could replace phosphates in a lot of syntheses, but this way was essentially devoted to layered compounds in order to increase the distance between the layers, and not with the aim of obtaining porous compounds. They mainly used monophosphonates, but some further attempts with diphosphonates or functionalized monophosphonates lead to pillared compounds which sometimes offer frameworks with an open structure. Using this way, we recently characterized [77] a porous vanadium(IV) diphosphonate (NH4)2(H20)2(V0) (V0(H20))2 (03P—CH2—P03)2 or MIL-2 (for Materials of Institut Lavoisier) in which the channels are occupied with water molecules and ammonium ions (Fig. 15 (left)). 

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