VPI-5: The first molecular sieve with pores larger than 10 Ångstroms

doi:10.1016/S0144-2449(88)80172-6

Zeolites

Volume 8, Issue 5, September 1988, Pages 362-366

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The adsorption properties of a novel family of aluminophosphate based molecular sieves denoted as VPI-5 are described. These molecular sieves are the first to contain pores larger than 10 Å. The large pores of the VPI-5 sieves consist of channels circumscribed by eighteen membered rings and possess free diameters of approximately 12–13 Å. The VPI-sieves are capable of adsorbing molecules excluded from other molecular sieves.

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Cited by (162)

Exploring the boundaries of molecular sieve materials
2023, Microporous and Mesoporous Materials
The Davis research program is focused on exploring and moving the boundaries of molecular sieve properties. Here, it is described how the program approached the investigation of: (i) extra-large pores and extra-large pore spaces, (ii) framework charge and (iii) enantiomerically enriched, powdered samples. Additionally, current work on item (iii), and site-specific placement of heteroatoms into the framework are discussed. The Corma research program also investigates a number of these areas, and some of the intersections with the Davis research program are provided.
Exploring the boundaries of molecular sieve materials
2022, Microporous and Mesoporous Materials
Citation Excerpt :
Several investigators claimed that VPI-5 was actually H1 [21]. We did discuss this point early in our publications on VPI-5 [22]. While there are a number of similar powder X-ray diffraction (XRD) peaks, we clearly showed that VPI-5 did NOT transform to tridymite upon heating like H1, but rather converted to AlPO4-8 if water was present.
The Davis research program is focused on exploring and moving the boundaries of molecular sieve properties. Here, it is described how the program approached the investigation of: (i) extra-large pores and extra-large pore spaces, (ii) framework charge and (iii) enantiomerically enriched, powdered samples. Additionally, current work on item (iii), and site-specific placement of heteroatoms into the framework are discussed. The Corma research program also investigates a number of these areas, and some of the intersections with the Davis research program are provided.
An in-situ x-ray diffraction and infrared spectroscopic study of the dehydration of AlPO<inf>4</inf>-54
2020, Solid State Sciences
Citation Excerpt :
AlPO4-54•xH2O, also known as VPI-5, with the VFI structure type [1] is the aluminophosphate with the largest pores [2].
The dehydration of the large pore aluminophosphate AlPO₄-54•xH₂O was studied in situ as a function of vacuum pressure at room temperature by infrared spectroscopy and x-ray diffraction. On polycrystalline samples, under primary vacuum, the adsorbed water is removed very rapidly. The structural water in the AlO₆ octahedra is then removed slowly with the quantity of the fully dehydrated form gradually increasing from 43 to 65% of the total material. This results in a two-phase mixture of fully dehydrated and a distinct partially dehydrated AlPO₄-54•1/2H₂O phase containing structural water. These phases have almost identical a cell parameters and very close c parameters. Secondary vacuum increases the amount of fully dehydrated material to more than 76%. Prolonged heating under vacuum increases the amount of fully dehydrated material to 90%. On single crystal samples, removal of adsorbed water is slower and results in a reduction in crystal quality, however prolonged exposure to primary vacuum yielded fully dehydrated material without the need for heating. The monoclinic structure of anhydrous AlPO4-54, space group Cm, with a doubled unit cell was confirmed using single crystal synchrotron x-ray diffraction data.
Sulfonium-based organic structure-directing agents for microporous aluminophosphate synthesis
2019, Microporous and Mesoporous Materials
Sulfur-centered phenyl, n-butyl, p-tolyl, and benzyl sulfoniums and sulfides were tested as organic structure-directing agents (SDAs) for the synthesis of crystalline microporous aluminophosphates (AlPOs) over various ranges of gel compositions, hydrothermal treatment temperatures, and crystallization times. Among the investigated compounds, triphenylsulfonium gave single-phase products of ATS-type AlPO and silicoaluminophosphate. Other sulfoniums yielded only non-porous, dense crystalline AlPOs. On the other hand, diaryl sulfides gave a tiny amount of AFI-type AlPO amid tridymite and amorphous phases. Based on the results, it was found to be reasonable that weakly basic sulfide could hardly act as a zeotype SDA due to the low protonation to sulfonium at the present synthesis pH.
Synthesis variables and behavior of VPI-5: A review
2015, Microporous and Mesoporous Materials
Citation Excerpt :
In regard of VPI-5, all these factors are reviewed in this review. Davis et al. [10,11] reported first molecular sieve that was consisted of rings with greater than 12 T atoms (T is tetrahedrally coordinated atoms) and pores ⩾ 12 Å i.e. VPI-5 (Virginia Polytechnic Institute Number 5) which is from a novel family of aluminophosphate based molecular sieves. This framework contains rings consisting of 18 T atoms and pores ⩾ 12 Å although hypothetical molecular sieve with 18 or 24 T membered rings and one dimensional pore, had also been proposed [12,13] before the first synthesis of VPI-5.
This review summarizes certain cloudy issues around the large porous aluminophosphate VPI-5, which stressed all mineralogists to rethink about these issues of this zeotype, in the light of selected evidences. In this review, characteristics of VPI-5 are discussed for its tremendous behavior with various types of synthesis procedures and effect of all variables over crystallization, thermal stability of VPI-5 framework and product reproducibility. The characteristic diversity of VPI-5 is reviewed in such a way that this wide pore material will attain better applications at ground state. Different synthesis procedures were summarized with optimized synthesis conditions and role of variables is counted on the basis of their effect on product for understanding trend of variables which are very important for researchers who are seeking for synthesis of this large pore size zeotype.
Triptycene structure-directing agents in aluminophosphate synthesis
2015, Microporous and Mesoporous Materials
Citation Excerpt :
In addition to VPI-5, three unknown phases were synthesized. The extra-large pore aluminophosphate VPI-5 [14,15] is formed in the presence of 2,6,14-triaminotriptycene 1 at a synthesis composition of: 1.0 P2O5: 1.0 Al2O3: 0.65 2,6,14-triaminotriptycene: 80H2O @ 140 °C. The XRD pattern of this product can be seen in Fig. 2 [15].
The synthesis of aluminophosphates is investigated using a number of triptycene-based organic structure-directing agents (OSDA). These OSDAs are designed to synthesize extra-large pore and/or large cavity-containing molecular sieves. Starting from the hydrophobic triptycene molecule, OSDAs are prepared by introducing three amine-based centers that can be charged either by protonation in the acidic aluminophosphate reaction media or through quaternization. VPI-5 is synthesized using these tripytycene OSDAs, and the OSDAs are occluded inside the pores. This synthesis marks the first time VPI-5 has been made as a single phase with an OSDA occluded inside the framework of the as-made material that is not removed by simple washing with water or other solvents. Additionally, several other aluminophosphates with unknown structures are synthesized using these new OSDAs.

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^†: Present address: Universidad de Antioquia, Medellin, Colombia.

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VPI-5: The first molecular sieve with pores larger than 10 Ångstroms