Layered phosphate/phosphonate materials

Layered phosphate/phosphonate and phosphonate materials, obtained by substitution of the phosphate moiety by phosphonate groups, display interesting tunable hydrophilic/organophilic properties for adsorption processes. When Candida rugosa lipase (CRL) is simply equilibrated with zirconium phosphate and phosphonate [135,136], immobilization was demonstrated to take place at the surface of the microcrystals. However, because lipase exhibits a strong hydrophobic character, its uptake by zirconium phosphate and phosphonate was much more related to the hydrophobic/hydrophilic character of the supports than to the surface area properties. A higher uptake is observed for zirconium-phenylphosphonate (78 %)... 

Kumar, C.V. and Chaudhari A. (2003) Unusual thermal stabilities of some proteins and enzymes bound in the galleries of layered alpha-Zr(IV) phosphate/phosphonates. Microporous and Mesoporous Materials, 57,181-190. 

A. Zr(IV) Phosphates and Phosphonates Layered, Porous, Inorganic Materials... 

Lamellar or linear structures are also formed by various other metal ions, such as zinc, (268) manganese, (269) molybdenum, (270) and vanadium (271,272). Among these other solids, vanadium derivatives attracted significant attention due to their potential as industrial catalysts. The structures of the metal phosphonates are similar to those of the corresponding phosphates, in a manner similar to the zirconium phosphate/phosphonates. Polymerization of phenylphosphonate, for example, with Mo(IV) resulted in a linear double-stranded structure where the phenyl groups are positioned on the outside of the linear structure (273). These other metal derivatives are bound to yield many future investigations regarding the fundamental and applied chemistry of layered materials. 

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)). 

Depending on the final purpose of the material, the appropriate pillar can be chosen. This flexibifity in the PILC synthesis is one of the main advantages compared to other porous substrates, such as zeofites, which have one definite pore size. The technique not only focuses on clays, but other layered structures serve as host materials as well. Examples are layered double hydroxides (anionic clays), metal(IV)- phosphates and phosphonates,layered silicic acids, etc. [4,5]. 

Polyethylene oxides and polyethyleneimines are of great interest because of their ability to form a wide variety of metal and salt complexes. We have anchored polyethylene oxide oligomers (n=l-33) and polyimines (n=l-4) to zirconium phosphate type layers. The polymers are first converted to phosphates or phosphonates which in turn react with Zr(IV) solutions to form the layered derivatives. Cross-linking of the layers has also been accomplished. Preliminary structural and complexing behavior of these layered materials is presented. It is demonstrated that the NaSCN-polyethyleneoxide... 

Tetravalent metal phosphonates, or MELS (for Molecularly Engineered Layered Structures), provide a novel class of materials that combine many of the properties of incn-ganic metal oxides with the organic functionality more commonly found in functionalized polymeric resins. Early development work on these materials was carried out by Alberti and co-woikers [ref. 1] and Dines et al. [ref. 2]. Synthesis and characterization of related zirconium phosphates that also contain phosphonate groups as pillars have been described by Clearfield [ref 3]. There is a substantial patent estate for tetravalent metal phosphonates, and exclusive rights to this estate are owned by Catalytica [ref 4]. 

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