Absolute configuration and domain structure of AlPO4-5 studied by single crystal X-ray diffraction

Klap, G.J.; Koningsveld, H. van; Graafsma, H.; Schreurs, Antoine M. M.

doi:10.1016/s1387-1811(00)00161-x

Cited by 40 publications

(48 citation statements)

References 14 publications

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“…Klap et al have shown in a series of papers [24][25][26] that the Al À O À P vector (of the T À O À T bonds parallel to c) always points in the same direction (in fact, AFI crystal growth only takes place in that direction), thus giving a permanent polarisation to the crystal along the c direction. This macroscopic polarisation may cause the alignment of the water molecules in the 6-MR channels.…”

Section: Resultsmentioning

confidence: 99%

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Gómez‐Hortigüela

Pérez‐Pariente

Corà

2009

Chemistry A European J

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A combination of experimental characterisation techniques and computational modelling has allowed us to gain insight into the molecular features governing structure direction in the synthesis of microporous aluminophosphates. The occlusion of three different structure-directing agents (SDAs), triethylamine (TEA), benzylpyrrolidine (BP) and (S)-(-)-N-benzylpyrrolidine-2-methanol (BPM), within the AFI structure during its crystallisation, together with the simultaneous incorporation of water, has been experimentally measured. We found a higher incorporation of organic molecules in the structure obtained with BPM, while a higher water (and lower organic) content is found for the ones obtained with TEA and BP as SDAs. The computational study provides a thermodynamic explanation for the observed behaviour in terms of the relative stabilisation energy of the SDAs and water molecules within the AFI framework compared with when they are in aqueous solution, and demonstrates that a competition for preferential occupation exists between water and organic SDAs, which is a function of the interaction with the inorganic framework. The lower interaction of TEA and BP molecules with the AFI structure promotes the simultaneous incorporation of water molecules in the 12-membered-ring (MR) channel, to increase the host-guest interaction energy and thus the thermodynamic stability. The presence of strongly interacting methanol groups in the BPM molecules leads to the incorporation of only organic molecules within the 12-MR channels. Our results demonstrate the essential role that water molecules play in the stabilisation of hydrophilic microporous aluminophosphates; a minimum amount of organic SDA is, however, essential for a templating role of the microporous architecture.

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Section: Resultsmentioning

confidence: 99%

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Gómez‐Hortigüela

Pérez‐Pariente

Corà

2009

Chemistry A European J

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“…a AlPO4-5 (P6cc): a ) b ) 13.718 Å, c ) 8.4526 Å. Al: 1O at 1.718 Å, 1O at 1.713 Å, 1O at 1.732 Å, 1O at 1.672 Å, 2P at 3.089 Å, 1P at 3.119 Å, 1P at 3.143 Å,1 Al at 4.051 Å. 21,22 large decrease in the intensity of the broad peak located at around 1.9 Å, corresponding to the first oxygen shell. This observation points toward a large reduction in the oxygen coordination number.…”

Section: Resultsmentioning

confidence: 99%

Unusual Coordination Behavior of Cr³⁺ in Microporous Aluminophosphates

et al. 2005

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A CrAPO-5 molecular sieve has been investigated with X-ray absorption spectroscopy (EXAFS-XANES) as dehydrated material and after loading with water and ammonia to unravel the coordination geometries of Cr 3+ in the framework of a microporous crystalline aluminophosphate, more particularly of the AFI-type. A comparison of the XANES data, a preedge analysis with crystal field multiplet calculations and EXAFS data, pointed toward the presence of framework Cr 3+ which, on dehydration, takes on a distorted tetrahedral coordination state. Due to the 3d 3 configuration of Cr 3+ , this unusual tetrahedral coordination environment strongly tends to transform into the more stable 6-fold coordination geometry by binding two extraframework water molecules during hydration. In the presence of ammonia, tetrahedral Cr 3+ readily transforms into a 5-fold coordination geometry by binding one ammonia molecule. Therefore, depending on the environmental conditions, the Cr 3+ ions can occur in a 4-, 5-, or 6-fold coordination. This observation underlines the flexibility of transition metal ions, such as Cr 3+ , to cope with unusual coordination geometries in inorganic hosts, making them interesting as potential active sites in heterogeneous catalysis.

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“…In the AlPO-5 unit cell, there are 24 equivalent tetrahedral sites (T) equally occupied by P and Al. Furthermore, there are four types of oxygen ions: O 1 and O 3 connect Al and P to form the 12-MRs, O 2 connects the 12-MR sheets along the c direction, and O 4 links the 12-MRs into the 4-MRs and 6-MRs sheets, which are perpendicular to the c direction [17]. In the acidic structure models, the proton was attached to O 3 .…”

Section: Structural Models and Computational Detailsmentioning

confidence: 99%

The acidic properties of H-MeAlPO-5 (Me=Si, Ti, or Zr): A periodic density functional study

Elanany¹,

Vercauteren²,

Kubo³

et al. 2006

Journal of Molecular Catalysis A: Chemical

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Absolute configuration and domain structure of AlPO4-5 studied by single crystal X-ray diffraction

Cited by 40 publications

References 14 publications

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Unusual Coordination Behavior of Cr³⁺ in Microporous Aluminophosphates

The acidic properties of H-MeAlPO-5 (Me=Si, Ti, or Zr): A periodic density functional study

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Absolute configuration and domain structure of AlPO4-5 studied by single crystal X-ray diffraction

Cited by 40 publications

References 14 publications

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Unusual Coordination Behavior of Cr3+ in Microporous Aluminophosphates

The acidic properties of H-MeAlPO-5 (Me=Si, Ti, or Zr): A periodic density functional study

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Unusual Coordination Behavior of Cr³⁺ in Microporous Aluminophosphates