Layered double hydroxides anionic exchange

The structure of the layered double hydroxides is the reverse of that of the clays. They are anionic materials in which the sheets are intercalated with anions instead of cations. These ions can be exchanged with several different anions. The cationic nature of the layers lends itself to pillaring by large Keg-gin anions. 

Layered double hydroxides (LDH), also referred to as anionic clays, are very useful materials due to their anion exchange properties. LDH display a layered structure built on a stacking of positive layers ([MII1 MIII (OH)2] +), separated by inter-lamellar domains constituted of anions and water molecules ([X e nH20]x ) [117]. 

The dispersion and solid-state ion exchange of ZnCl2 on to the surface of NaY zeolite by use of microwave irradiation [17] and modification of the surface of active carbon as catalyst support by means of microwave induced treatment have also been reported [18]. The ion-exchange reactions of both cationic (montmorillonites) and anionic clays (layered double hydroxides) were greatly accelerated under conditions of microwave heating compared with other techniques currently available [19.]... 

A further example of ion-exchange of an organometallic complex onto a layered support has been provided by the anion exchange of a sulfonated ruthenium BINAP complex onto the external surface of layered double hydroxides [119]. Although achvihes and enantioselechvities for the hydrogenation of dimethyl itaconate were comparable to the homogeneous catalyst, and catalyst deactivation was not detected, with geraniol as substrate, catalyst deactivation was unavoidable. 

Jacobs, P.A. (1997) The Immobilization of Sulfonated Ru-EINAP Chloride by Anion Exchange on Layered Double Hydroxides, Studies in Surface Science Catalysis,... 

Parvulescu et al. noted an interesting change in EG telomer product selectivity upon immobilization of an Pd/TPPTS catalyst on a basic support [58]. In an attempt to address the issues associated with recovery and reuse of the telomerization catalyst, the anionic TPPTS ligand was immobilized on various layered double hydroxides by ion exchange methods (Scheme 11). The use of these catalysts in the telomerization of methanol and ethylene glycol resulted in a remarkable shift in... 

Anion exchange Amberlite IRA 900 Polyvinylpyridinium polymer Layered double hydroxides Sulfonated porphyrins, phthalocyanines Sorokin and Meunier (112), Mirkhani et al. (113) Labat and Meunier (114) Chibwe and Pinnavaia (115)... 

Meyn, M., Beneke, K., and Legaly, G. Anionic-exchange reactions of layered double hydroxides, Inorg. 

Kaneyoshi, M. and Jones, W. (1998). Exchange of interlayer terephthalate anions from a Mg-Al layered double hydroxide formation of intermediate interstratihed phases. Chem. Phys. Lett. 296, 183. 

Fogg, A. M., Dunn, J. S. and O Hare, D. (1998). Formation of second-stage intermediates in anion-exchange intercalation reactions of the layered double hydroxide [LiAl2(OH)6]Cl, H20 as observed by time-resolved, in situ X-ray diffraction. Chem. Mater. 10, 356. 

Mousty, C., Therias, S., Forano, C. and Besse, J. P. (1994). Anion-exchanging clay-modified electrodes - synthetic layered double hydroxides intercalated with electroactive organic-anions. J. Electro anal. Chem. 374, 63. 

Anionic clays are natural or synthetic lamellar mixed hydroxides with interlayer spaces containing exchangeable anions [10, 104]. The generic terms, layered double hydroxides (LDHs) or hydrotalcites are widely used, the latter because exten-... 

Layered double hydroxides with the hydrotalcite stmcture were synthesized with varying Mg A1 atomic ratios and with different contents of exchangeable CT and CO3 anions. The CO2 adsorption isotherms showed an increase of the uptake and consequently of the basicity with initial CO content and calcination temperature up to 800 K. Increasing the Mg A1 ratio of the hydrotalcites from 2.33 to 3 resulted in an increase of the total number of basic sites [94]. 

Layered double hydroxides (LDHs) are a unique type of clay with anion exchange capacity. In nature, they are found in the carbonated hydrotalcite-like compounds... 

Liu, Z.P., Ma, R.Z., Osada, M., lyi, N., Ebina, Y., Takada, K., and Sasaki, T. 2006. Synthesis, anion exchange, and delamination of Co-Al layered double hydroxide Assembly of the exfoliated nanosheet/polyanion composite films and magneto-optical studies. Journal of the American Chemical Society 128. 4872-4880. 

The Immobilization of Sulfonated Ru-BINAP Chloride by Anion Exchange on Layered Double Hydroxides... 

Such layered double hydroxides can also serve as hosts for guests, such as carboxylates, sulfates, phosphates, porphyrins, and polyoxometallates that can be put in by anion exchange.85... 

The layered double hydroxides have been of interest as anion exchangers, basic catalysts, and catalyst precursors. Pillared derivatives of the type discussed earlier for the clays have been synthesized by ion exchange with polyoxometallate anions but have lower thermal stability. Several authors have reported synthesis of layered double hydroxides pillared with the Vio028 ion by direct ion exchange or by techniques that involve preswelling the layer structure with an organic anion. For example, the terephthalate anion was used in the synthesis ofVio028 and Mo7 024 intercalated phases. 

---