Aluminophosphates, mesoporous

Solid-state NMR spectroscopy was used for studying the formation of cubic mesoporous aluminophosphate thin films and powders. The analysis of the initial gel, the as-deposited materials and the thermally-treated materials elucidated the changes in the coordination of phosphorus and aluminium atoms and thus revealed how the framework formation and condensation proceeds. The consolidation process in thin films was different than the process in powders. Most probably this could be attributed to the effect of glass substrate. 

Keywords mesoporous aluminophosphates, thin films, NMR spectroscopy... 

Figure 2.31P and 27AI MAS NMR spectra of F127- and FI 08-templated cubic large-pore mesoporous aluminophosphate thin films. 

The acidity of thermally stable mesoporous aluminophosphates (AlPO) and sili-coaluminophosphates (SAPO) has also been stndied by microcalorimetry [245]. By contrast with microporous crystalline alnminophosphate molecnlar sieves, mesoporous compounds are amorphous and characterized by Al/P ratios greater than 1. These particularities are responsible for a strong Lewis acidity, making these mesoporous materials more acidic than the microporons analognes, with an amonnt of strong acid sites that increases with the silicon content. 

Because of the similarity between aluminophosphate and silica molecular sieves, the synthesis of mesoporous silica was soon followed by the efforts aimed toward the synthesis of mesoporous aluminophosphates. Both lamella and hexagonally ordered aluminophosphate mesostructures have been prepared. ... 

The synthesis of the fragment CpTi supported on a mesoporous aluminophosphate has been described the coordination mode of the CpTi(iv) fragment is as depicted in Scheme 414.994... 

Coordination of the Cp2Ti fragment to a mesoporous aluminophosphate (Scheme 613) has been described and the bonding of the Ti(iv) centers has been studied.994... 

Early efforts towards these resulted only in the production of lamellar aluminophosphates. Later, mesoporous aluminophosphates were synthesized successfully by using CTAB or CTAC as template and Al( PO)3 or Al(OH)3 as aluminum source.12411... 

L.M. Wang, B.Z. Tian, H. Fan, X.Y. Liu, H.F. Yang, C.Z. Yu, B. Tu, and D.Y. Zhao, Block Copolymer Templating Synthese of Ordered Large-pore Stable Mesoporous Aluminophosphates and Fe-aluminophosphate Based on an Acid-Base Pair Route. Microporous Mesoporous Mater., 2004, 67, 123-133. 

Titanium substituted hexagonal mesoporous aluminophosphate (Ti-HMA) molecular sieves, which exhibit excellent performance in the oxidation of cyclohexanone to Ol/One with HP (yielding mainly cyclohexanol), or t-BuOOH (mainly cyclohexanone) or oxygen (mainly cyclohexanol). Similar performance is obtained... 

A remarkable discovery of mesoporous silicates with pore openings from 2 to 50 nm in 1991 was quickly followed by a successful preparation of mesoporous aluminophosphates with hexagonal pore arrangement and amorphous nature of the framework (12-15). Up to date, a variety of silicon- and metal-substituted mesoporous aluminophosphate materials with different incorporated metal... 

Mesoporous Aluminophosphates. The structure classification of amorphous mesoporous aluminophosphates is based on the pore arrangement that can be hexagonal, cubic, or disordered. Aluminum species in these materials are usually present as both four- and six-coordinated species, whereas phosphate units being always tetrahedral. The Al/P ratio differs from unity due to the uncompleted condensation of the mesoporous framework (16). 

Hexagonal mesoporous aluminophosphates have pores arranged in the p6m symmetry as shown in Figure 9, analogous to MCM-41 mesoporous silicate (82). 

Table 2. Structural and Compositional Data on Hexagonal and Cubic Mesoporous Aluminophosphates... 

Fig. 9. Hexagonal arrangement of the pore in the mesoporous aluminophosphate with the p6m symmetry TEM image viewed in [001] direction and schematic presentation of...

Cubic mesoporous aluminophosphates have been so far prepared only as thin film and posses Im3m symmetry of the pores (Figure 10). No other... 

Some other synthetic routes reported recently resulted in the formation of thermally stable mesoporous aluminophosphates (Figure 11) however, most of them lack pore ordering (Table 3). 

The most recent reviews on mesoporous aluminophosphates have been done by Kimura (16) and Pastore (65) in 2005. 

Iron-substituted mesoporous aluminophosphate was used as a novel, efficient and ecofriendly catalyst for reductive cleavage of azo dyes and reduction in nitroarenes and catalytic transfer hydrogenation of nitro and carbonyl compounds. Unlike most of the iron-containing molecular sieves, dislodgement of tetrahedral Fe(III) was not observed upon various process treatments such... 

Gianotti, E., Oliveira, E.C., Coluccia, S., Pastore, H.O., and Marchese, L. (2003) Synthesis and surface properties of Ti-containing mesoporous aluminophosphates a comparison with Ti-grafted mesoporous silica Ti-MCM-41. Inorg. Chim. Acta, 349, 259-264. 

Proposed synthesis mechanism for the hierarchically porous aluminophosphates (HP-AIPO-n) with TPHAC as the mesopore-directing agent. Reproduced from Choi M, Srivastava R, Ryoo R. OrganosHane surfactant-directed synthesis of mesoporous aluminophosphates constructed with crystalline microporous frameworks. Chem Commun 2006 4380-4382 with permission of The Royal Society of Chemistry. 

Choi M, Srivastava R, Ryoo R. OrganosUane surfactant-directed synthesis of mesoporous aluminophosphates constructed with crystaUine microporous frameworks. Chem Commun 2006 4380-2. 

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