A Comparative-Study of the Microporosity of the Ammonium and Cesium Salts of 12-Tungstophosphoric, 12-Molybdophosphoric, and 12-Tungstosilicic Acids by Xe129 NMR

Bonardet, J.L.; Fraissard, J.; McGarvey, G.B.; Moffat, J.B.

doi:10.1006/jcat.1995.1017

Cited by 29 publications

(9 citation statements)

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“…Moffat et al reported the value of ca. 2.0 nm by applying the MP methods and 0.9 nm by 129 Xe NMR for the size of micropore of (NH 4 ) 3 PW 12 O 40 . Our results for the aggregates are close to the latter value, although interpretations about the origin of the micropores are different (see above).…”

Section: Discussionmentioning

confidence: 99%

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

1997

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It was demonstrated that porous aggregates of (NH4)3PW12O40 nanocrystallites were formed by epitaxial self-assembly, when dodecatungstophosphoric acid was precipitated by ammonium hydrogen carbonate in an aqueous solution. Scanning electron microscopy combined with nitrogen and argon adsorption measurements showed that nanocrystallites of (NH4)3PW12O40 formed aggregates of ca. 0.3−1 μm in size, which are porous with a nearly uniform micropore size of 0.6−1.3 nm in diameter. The shape of these aggregates changed from spherical to symmetric dodecahedral as the precipitation temperature increased. Electron diffraction, transmission electron microscopy, and X-ray powder diffraction demonstrated that the nanocrystallites which form the aggregates had the same crystal orientation in each aggregate, leaving pores between the nanocrystallites, and they were connected epitaxially to each other to variable extents, depending on the precipitation temperature. The dodecahedral aggregates, for which the epitaxial interconnections grow significantly, can be regarded as microporous single crystals. The results were compared with the aggregates of Cs salts which were previously shown to be randomly oriented and exhibit shape-selective catalysis.

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Section: Discussionmentioning

confidence: 99%

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

1997

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“…For isostructural compounds, see: Boeyens et al (1976); Goubin et al (2004); Kang et al (2004); Parent & Moffat (1996). For properties and applications of compounds with Keggin anions, see: Bonardet et al (1995); Clemente-Lé on et al (1997); Katsoulis (1998); Ló pez et al (2001); Maestre et al (2001). Keggin anions were described for the first time by Keggin (1933 Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED; program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007); program(s) used to refine structure: CRYSTALS (Betteridge et al, 2003); molecular graphics: CAMERON (Watkin et al, 1996) and DrawXtl (Finger et al, 2007); software used to prepare material for publication: CRYSTALS.…”

Section: Related Literaturementioning

confidence: 99%

“…(Keggin, 1933), [XM 12 O 40 ] nwith X a main group or a transition metal ion and M a transition metal ion, have been largely studied from a fundamental point of view (López et al, 2001;Maestre et al, 2001) and also because of of their applications in view of their interesting redox properties in relation to their micro-porosity in the salts of Keggin anions with various cations (Bonardet et al, 1995;Clemente-Léon et al, 1997;Katsoulis et al, 1998). (Keggin, 1933), [XM 12 O 40 ] nwith X a main group or a transition metal ion and M a transition metal ion, have been largely studied from a fundamental point of view (López et al, 2001;Maestre et al, 2001) and also because of of their applications in view of their interesting redox properties in relation to their micro-porosity in the salts of Keggin anions with various cations (Bonardet et al, 1995;Clemente-Léon et al, 1997;Katsoulis et al, 1998).…”

Section: Related Literaturementioning

confidence: 99%

Rb₃[PMo₁₂O₄₀], a compound containing Keggin anions

2007

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Key indicators: single-crystal X-ray study; T = 293 K; mean (P-O) = 0.005 Å; R factor = 0.032; wR factor = 0.086; data-to-parameter ratio = 18.3.The cubic structure of trirubidium molybdophosphate, Rb 3 [PMo 12 O 40 ], contains -type Keggin [PMo 12 O 40 ] 3À anions and Rb + counter-ions located in orthogonally intersecting channels. The P and Rb atoms are located on special positions with site symmetries 43m and 42.m, respectively. The threedimensional arrangement is isostructural with that found in, for example, X 3 [PMo 12 O 40 ], with X = K, NH 4 and H 3 O, or X 3 [PW 12 O 40 ] and X 4 [SiW 12 O 40 ], with X = Ag and Tl. The compound was crystallized using a typical high-temperature solid-state reaction with GaPO 4 and X 3 Mo 3 O 10 (X = Rb or Li) as starting materials.

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“…[10,11]. These HPA salts exhibit microporous/mesoporous structures and larger surface area than the pure acids [12,13]. The acidic Cs + salt, Cs 2.5 H 0.5 PW 12 O 40 , was demonstrated as an excellent solid catalyst for various reactions [12,14].…”

Section: Introductionmentioning

confidence: 99%

Progress of the Application of Mesoporous Silica-Supported Heteropolyacids in Heterogeneous Catalysis and Preparation of Nanostructured Metal Oxides

Ren

Yue

et al. 2010

Materials

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Mesoporous silica molecular sieves are a kind of unique catalyst support due to their large pore size and high surface area. Several methods have been developed to immobilize heteropolyacids (HPAs) inside the channels of these mesoporous silicas. The mesoporous silica-supported HPA materials have been widely used as recyclable catalysts in heterogeneous systems. They have shown high catalytic activities and shape selectivities in some reactions, compared to the parent HPAs in homogeneous systems. This review summarizes recent progress in the field of mesoporous silica-supported HPAs applied in the heterogeneous catalysis area and preparation of nanostructured metal oxides using HPAs as precursors and mesoporous silicas as hard templates.

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A Comparative-Study of the Microporosity of the Ammonium and Cesium Salts of 12-Tungstophosphoric, 12-Molybdophosphoric, and 12-Tungstosilicic Acids by Xe129 NMR

Cited by 29 publications

References 0 publications

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Rb₃[PMo₁₂O₄₀], a compound containing Keggin anions

Progress of the Application of Mesoporous Silica-Supported Heteropolyacids in Heterogeneous Catalysis and Preparation of Nanostructured Metal Oxides

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A Comparative-Study of the Microporosity of the Ammonium and Cesium Salts of 12-Tungstophosphoric, 12-Molybdophosphoric, and 12-Tungstosilicic Acids by Xe129 NMR

Cited by 29 publications

References 0 publications

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH4)3PW12O40: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH4)3PW12O40: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Rb3[PMo12O40], a compound containing Keggin anions

Progress of the Application of Mesoporous Silica-Supported Heteropolyacids in Heterogeneous Catalysis and Preparation of Nanostructured Metal Oxides

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Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Rb₃[PMo₁₂O₄₀], a compound containing Keggin anions