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152. High-field 95Mo and 183W static and MAS NMR study of polyoxometalates.

Author

Haouas, Mohamed, Trébosc, Julien, Roch‐Marchal, Catherine, Cadot, Emmanuel, Taulelle, Francis, and Martineau‐Corcos, Charlotte

Subjects
*MOLYBDENUM isotopes, *TUNGSTEN isotopes, *NUCLEAR magnetic resonance spectroscopy, *POLYOXOMETALATES, *CRYSTAL structure, *SOLID state chemistry
Abstract

The potential of high-field NMR to measure solid-state 95Mo and 183W NMR in polyoxometalates (POMs) is explored using some archetypical structures like Lindqvist, Keggin and Dawson as model compounds that are well characterized in solution. NMR spectra in static and under magic angle spinning (MAS) were obtained, and their analysis allowed extraction of the NMR parameters, including chemical shift anisotropy and quadrupolar coupling parameters. Despite the inherent difficulties of measurement in solid state of these low-gamma NMR nuclei, due mainly to the low spectral resolution and poor signal-to-noise ratio, the observed global trends compare well with the solution-state NMR data. This would open an avenue for application of solid-state NMR to POMs, especially when liquid-state NMR is not possible, e.g., for poorly soluble or unstable compounds in solution, and for giant molecules with slow tumbling motion. This is the case of Keplerate where we provide here the first NMR characterization of this class of POMs in the solid state. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2017
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153. Investigation of the protonation state of the macrocyclic {HnP8W48O184} anion by modeling 183W NMR chemical shifts.

Author

Haouas, Mohamed, Diab, Manal, Moussawi, Mhamad Aly, Cadot, Emmanuel, Floquet, Sébastien, Henry, Marc, and Taulelle, Francis

Subjects
*NUCLEAR magnetic resonance, *CHEMICAL shift (Nuclear magnetic resonance), *POLYOXOTUNGSTATES, *PROTON transfer reactions, *OXO compounds
Abstract

A semi-empirical approach based on the partial charge formalism has been used to calculate 183W NMR chemical shifts in polyoxotungstates (POTs). Good consistency between calculations and experimental measurements allowed determining the main effective parameters for modeling the electronic state of the {WVIO6} centers. As the three 183W NMR chemical shifts of the {P8W48O184} macrocycle exhibit strong pH dependence, partial charge model calculations have been carried out for the investigation of the protonation of the metal–oxo framework. Furthermore, these calculations highlight the effect of the potassium ions embedded within the internal cavity. In this work, NMR parameters were computed using the PACHA software, distinguishing and assigning 183W NMR resonances. [ABSTRACT FROM AUTHOR]

Published
2017
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154. Self-assembly of [PNbxW12−xO40]n− Keggin anions – a simple way to mixed Nb–W polyoxometalates.

Author

Abramov, Pavel A., Shmakova, Alexandra A., Haouas, Mohamed, Fink, Gerhard, Cadot, Emmanuel, and Sokolov, Maxim N.

Subjects
KEGGIN anions, TUNGSTATES, POLYOXOMETALATES
Abstract

This paper summarizes preparations of mixed phosphoniobotungstates [PNbxW12−xO40](3+x)− (x = 1–3) in two different ways: (i) incorporation of Nb into pre-existing lacunary phosphotungstates and (ii) self-assembly reactions. A niobium oxalate complex as the source of niobium is used. The reaction products were monitored by 31P and 183W NMR in solution as well as by 31P MAS NMR techniques for precipitated samples. Single-substituted species [PNbW11O40]4− forms rapidly and selectively from lacunary [PW11O39]7− with one equivalent of [NbO(C2O4)2(H2O)2]−. With the increasing amount of the niobium oxalate the highest number of Nb atoms was found to be three per Keggin anion, but the disubstituted [PNb2W10O40]5− was always the preferable product whatever the tungsten reagent was. The reaction products with x = 2 and 3 are present as mixtures of all possible isomers, but the ratio between the individual isomers depends on the synthetic pathway. [ABSTRACT FROM AUTHOR]

Published
2017
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155. Correction to “Hierarchization of USY Zeolite by NH4OH. A Postsynthetic Process Investigated by NMR and XRD”

Author

Van Aelst, Joost, primary, Haouas, Mohamed, additional, Gobechiya, Elena, additional, Houthoofd, Kristof, additional, Philippaerts, An, additional, Sree, Sreeprasanth Pulinthanathu, additional, Kirschhock, Christine E. A., additional, Jacobs, Pierre, additional, Martens, Johan A., additional, Sels, Bert F., additional, and Taulelle, Francis, additional

Published
2014
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156. Hierarchization of USY Zeolite by NH4OH. A Postsynthetic Process Investigated by NMR and XRD

Author

Van Aelst, Joost, primary, Haouas, Mohamed, additional, Gobechiya, Elena, additional, Houthoofd, Kristof, additional, Philippaerts, An, additional, Sree, Sreeprasanth Pulinthanathu, additional, Kirschhock, Christine E. A., additional, Jacobs, Pierre, additional, Martens, Johan A., additional, Sels, Bert F., additional, and Taulelle, Francis, additional

Published
2014
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159. Tracking “Apolar” NMe4+ Ions within Two Polyoxothiomolybdates that Have the Same Pores: Smaller Clathrate and Larger Highly Porous Clusters in Action

Author

Korenev, Vladimir S., primary, Boulay, Antoine G., additional, Haouas, Mohamed, additional, Bannani, Fatma, additional, Fedin, Vladimir P., additional, Sokolov, Maxim N., additional, Terazzi, Emmanuel, additional, Garai, Somenath, additional, Müller, Achim, additional, Taulelle, Francis, additional, Marrot, Jérôme, additional, Leclerc, Nathalie, additional, Floquet, Sébastien, additional, and Cadot, Emmanuel, additional

Published
2014
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161. pH-Controlled One Pot Syntheses of Giant Mo2O2S2-Containing Seleno-Tungstate Architectures

Author

Moussawi, Mhamad Aly, Floquet, Sébastien, Abramov, Pavel A., Vicent, Cristian, Haouas, Mohamed, and Cadot, Emmanuel

Abstract

Self-assembly reactions of Na2WO4, SeO2/SeO32–, and [Mo2O2(μ-S)2(H2O)6]2+give, depending on the pH value, two new large polyoxometalate complexes: i.e., [(γ-Se2W14O52)3(Mo2O2(μ-S)2(H2O)2)6]24–(1) isolated at pH 3.5 and [(γ-Se2W14O52)4(WO3(H2O))8(W2O5)2(W4O12)2(Mo2O2(μ-S)2(H2O)2)4(Mo2O2(μ-S)2(SeO3))4]36–(2) isolated at pH 2. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in solution by ESI-MS and NMR.

Published
2018
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164. Properties of a Tunable Multinuclear Nickel Polyoxotungstate Platform

Author

El Moll, Hani, primary, Rousseau, Guillaume, additional, Dolbecq, Anne, additional, Oms, Olivier, additional, Marrot, Jérôme, additional, Haouas, Mohamed, additional, Taulelle, Francis, additional, Rivière, Eric, additional, Wernsdorfer, Wolfgang, additional, Lachkar, David, additional, Lacôte, Emmanuel, additional, Keita, Bineta, additional, and Mialane, Pierre, additional

Published
2013
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165. Catalyst Design by NH4OH Treatment of USY Zeolite.

Author

Van Aelst, Joost, Verboekend, Danny, Philippaerts, An, Nuttens, Nicolas, Kurttepeli, Mert, Gobechiya, Elena, Haouas, Mohamed, Sree, Sreeprasanth P., Denayer, Joeri F. M., Martens, Johan A., Kirschhock, Christine E. A., Taulelle, Francis, Bals, Sara, Baron, Gino V., Jacobs, Pierre A., and Sels, Bert F.

Subjects
CATALYSTS, ZEOLITES, ION exchange (Chemistry), MICROPOROSITY, CRYSTALLINITY
Abstract

Hierarchical zeolites are a class of superior catalysts which couples the intrinsic zeolitic properties to enhanced accessibility and intracrystalline mass transport to and from the active sites. The design of hierarchical USY (Ultra-Stable Y) catalysts is achieved using a sustainable postsynthetic room temperature treatment with mildly alkaline NH4OH (0.02 m) solutions. Starting from a commercial dealuminated USY zeolite (Si/Al = 47), a hierarchical material is obtained by selective and tuneable creation of interconnected and accessible small mesopores (2–6 nm). In addition, the treatment immediately yields the NH4+ form without the need for additional ion exchange. After NH4OH modification, the crystal morphology is retained, whereas the microporosity and relative crystallinity are decreased. The gradual formation of dense amorphous phases throughout the crystal without significant framework atom leaching rationalizes the very high material yields (>90%). The superior catalytic performance of the developed hierarchical zeolites is demonstrated in the acid-catalyzed isomerization of α-pinene and the metal-catalyzed conjugation of safflower oil. Significant improvements in activity and selectivity are attained, as well as a lowered susceptibility to deactivation. The catalytic performance is intimately related to the introduced mesopores, hence enhanced mass transport capacity, and the retained intrinsic zeolitic properties. [ABSTRACT FROM AUTHOR]

Published
2015
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170. ChemInform Abstract: Oxothiomolybdenum Derivatives of the Superlacunary Crown Heteropolyanion {P8W48}: Structure of [K4{Mo4O4S4(H2O)3(OH)2}2(WO2) (P8W48O184)]30-and Studies in Solution.

Author

Korenev, Vladimir S., primary, Floquet, Sebastien, additional, Marrot, Jerome, additional, Haouas, Mohamed, additional, Mbomekalle, Israel-Martyr, additional, Taulelle, Francis, additional, Sokolov, Maxim N., additional, Fedin, Vladimir P., additional, and Cadot, Emmanuel, additional

Published
2012
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173. Oxothiomolybdenum Derivatives of the Superlacunary Crown Heteropolyanion {P8W48}: Structure of [K4{Mo4O4S4(H2O)3(OH)2}2(WO2)(P8W48O184)]30– and Studies in Solution

Author

Korenev, Vladimir S., primary, Floquet, Sébastien, additional, Marrot, Jérôme, additional, Haouas, Mohamed, additional, Mbomekallé, Israël-Martyr, additional, Taulelle, Francis, additional, Sokolov, Maxim N., additional, Fedin, Vladimir P., additional, and Cadot, Emmanuel, additional

Published
2012
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176. Functionalization of Mo132 Keplerate Nanocapsules by Cyclic Carboxylates: L-proline vs Cyclopentanecarboxylate

Author

Awada, Mouhamad, Floquet, Sebastien, Haouas, Mohamed, Watfa, Nancy, Marrot, Jerome, Roch-Marchal, Catherine, Coeffard, Vincent, Greck, Christine, Bour, Christophe, Gandon, Vincent, Taulelle, Francis, and Cadot, Emmanuel

Abstract

Background: Keplerate-type capsules represent unique supramolecular objects displaying a tuneable spatially-restricted environment and are promising in many domains. In particular, some recent reports demonstrate that chemical transformations can occur specifically within the cavity, then acting as a nano-reactor. Some authors evidenced that the porous capsule provides internal active sites for catalytic transformation. In this idea, we recently succeeded to synthetize Keplerate capsules incorporating dicarboxylate anions, offering available coordination site for transition metals inside the Mo132 nanocapsule. Objectives: The aim of this study was to introduce a chiral ligand potentially relevant for organocatalysis inside the porous Keplerate nanocapsule, i.e. L-proline, which is known for promoting various activation modes in asymmetric aminocatalysis. Methods: The work described herein first focuses on the internal functionalization of the [(MoVI 6O21)12(MoV 2O4)30(H2O)72L30]n- nanocapsule with cyclopentanecarboxylate ligand which can be viewed as a model of L-proline in terms of size. FT-IR, X-ray diffraction and solution and solid-state NMR studies were performed in order to unambiguously evidence the formation of new Mo132 derivatives. In a second part, different strategies were attempted in solution to functionalize Mo132 capsules by L-proline. NMR studies in solid state and in solution were employed to monitor this process. Results: In this report, new cyclopentanecarboxylate-containing Keplerate compounds have been synthesized and characterized in the solid state and in solution. The 1D and DOSY 1H NMR spectra supported by X-ray crystallographic analysis are consistent with 22 to 25 ligands coordinated over the 30 {Mo2O4} linkers. Solid state 1H and 13C MAS NMR performed on the new described compound (NH4)50[Mo132O372(H2O)72(CPC)22(SO4)8]. 120H2O provided further characterizations of ligand substitution within the capsule by carboxylate ions. In a second part, the encapsulation of L-proline in Mo132 was investigated by different strategies. In solution, no substitution of sulfate or acetate ligands in the Mo132 precursors was observed in aqueous solution. DOSY 1H NMR studies evidenced that the cationic part of this molecule interacts with the surface of Mo132. A direct synthesis method was then attempted by mixing molybdate, L-proline and hydrazine in water at pH = 4. It led to an insoluble dark brown powder, for which the FT-IR spectrum, the elemental analysis and the solid state NMR are in agreement with a compound of formula (NH4)12[Mo132O372(H2O)132](L-proline)60 in which the L-proline are located outside the capsule and probably allow the formation of a network between L-proline molecules and ligand-free [Mo132O372(H2O)132]12- capsules. Conclusion: A new Keplerate compound has been discovered with cyclopentanecarboxylate ligands. Attempts for encapsulation of L-proline ligands within the cavity of Mo132 revealed unsuccessful but we isolated a powder with formula (NH4)12[Mo132O372(H2O)132](L-proline)60 in which the L-proline are located outside the capsule. It probably interacts with the surface of Mo132 capsule through the cationic part of this molecule, a phenomenon which surely competes with the encapsulation of the latter. Moreover, the low pKa value (1.95) of the carboxylate function of L-proline compared to that of the cyclopentanecarboxylate (4.90) appears as a second key criteria for the encapsulation or the non-encapsulation of ligands within the cavity of Keplerates.

Published
2017

177. MIL-101(Cr) MOF as a Support for Reactive Polyoxometalates (POMs) Clusters. Principles of POMs Encapsulation and Chemistry of POMs Inside MIL-101 Cavities

Author

Canioni, Romain, Roch-Marchal, Catherine, Haouas, Mohamed, Vimont, Alexandre, Horcajada, Patricia, Secheresse, Francis, and Serre, Christian

Abstract

Background: Incorporation of polyoxometalates (POMs) inside mesoporous materials such as Metal Organic Frameworks (MOFs) is a common strategy to prepare highly dispersed active species useful for catalytic applications. Nevertheless, a systematic study of the POMs insertion especially in MIL-101(Cr), one of the most used MOFs, appears necessary to clarify the nature of the species really incorporated. Objectives: Effects of the structure, charge and size of the POMs on the nature of inserted ionic species, their maximum loading, and their interaction with the MOF framework are investigated. Methods: POMs with the same Keggin structure (13 Å) but different charges were used, i.e., [PMo12O40]3-, [SiMo12O40]3-, [PMo11VVO40]4-, [PMo11VIVO40]5- with various counter-ions like H+, Na+, NH4 + or TBA+. Other compounds known for their stability and larger dimension were also used, namely the Dawson-type [PMo18O62]6-, the Preyssler-type [P5W30O110]15-, and the macro-ring [P8W48O184]40- with diameters of 15, 18 and 24 Å, respectively. MIL-101(Cr), chromium(III) terephthalate, synthesized in presence or absence of fluorhydric acid was used. Impregnation of POMs was performed in presence of a large excess of POMs to determine the maximum loading, or in proportion of the maximum loading. All compounds have been characterized by elemental analysis, infrared (IR), UV-Visible, and 31P NMR spectroscopies, X-Ray powder diffraction and thermo-diffractometry, and thermogravimetry. Textural properties of modified materials were also characterized using N2 adsorption isotherms. The POM interaction with the MOF was also investigated by in situ IR spectroscopy studies monitoring the adsorption of CO probe and the potential transformations of POM incorporated inside the cavities were studied. Results: All types of the counter ions of POMs are not incorporated inside the MOF, [Cr3Fx(H2O)3- xO(bdc)3](NO3)(1-x).nH2O ((bdc = benzene-1,4-dicarboxylate, x << 1), either in aqueous or organic solvent. Incorporation of POMs within the cavities of MIL-101(Cr) occurs by ionic exchange with nitrate ions. The maximum of POMs loading per large cavity depends on their negative charge, but also on the steric limitation of the structure type of POM: 8 for Keggin one and 4 for Dawson one. Thermodiffraction reveals an increase of the thermal stability of POM@MIL-101(Cr) until 280°C versus 220°C for the parent empty MOF. The study of CO adsorption by in situ IR spectroscopy indicates that the Lewis acid sites of MIL-101(Cr) are blocked by nitrate ions and incorporation of POM increases slightly their access. Furthermore, no significant Brønsted acid sites were detected. Subsequent ionic exchange of incorporated POMs with Cl-, ClO4 -, and other POMs were also studied. Finally, the pH stability of the MOF allows the partial hydrolysis of incorporated POM leading to unsaturated POM that can react with transition metal neutral complexes. Conclusion: No counter-ions of POMs are incorporated. Incorporation of POMs inside MIL-101(Cr) proceeds by ionic exchange. POMs thermally stabilize the MOF's framework and slightly increase the acess to Lewis acid sites. POMs can be removed by ionic exchange. We demonstrate that the host MIL- 101(Cr) behaves as a molecular reactor for the POMs chemistry.

Published
2017

181. Selective conversion of {Mo132} Keplerate ion into 4-electron reduced crown-capped Keggin derivative [Te5Mo15O57]8−. A key intermediate to single-phase M1 multielement MoVTeO light-alkanes oxidation catalyst

Author

Canioni, Romain, primary, Marchal-Roch, Catherine, additional, Leclerc-Laronze, Nathalie, additional, Haouas, Mohamed, additional, Taulèlle, Francis, additional, Marrot, Jérôme, additional, Paul, Sebastien, additional, Lamonier, Carole, additional, Paul, Jean-François, additional, Loridant, Stéphane, additional, Millet, Jean-Marc M., additional, and Cadot, Emmanuel, additional

Published
2011
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185. Influence of [Mo6Br8F6]2−Cluster Unit Inclusion within the Mesoporous Solid MIL-101 on Hydrogen Storage Performance

Author

Dybtsev, Danil, primary, Serre, Christian, additional, Schmitz, Barbara, additional, Panella, Barbara, additional, Hirscher, Michael, additional, Latroche, Michel, additional, Llewellyn, Philip L., additional, Cordier, Stéphane, additional, Molard, Yann, additional, Haouas, Mohamed, additional, Taulelle, Francis, additional, and Férey, Gérard, additional

Published
2010
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188. Occurrence of Uncommon Infinite Chains Consisting of Edge-Sharing Octahedra in a Porous Metal Organic Framework-Type Aluminum Pyromellitate Al4(OH)8[C10O8H2] (MIL-120): Synthesis, Structure, and Gas Sorption Properties

Author

Volkringer, Christophe, primary, Loiseau, Thierry, additional, Haouas, Mohamed, additional, Taulelle, Francis, additional, Popov, Dmitry, additional, Burghammer, Manfred, additional, Riekel, Christian, additional, Zlotea, Claudia, additional, Cuevas, Fermin, additional, Latroche, Michel, additional, Phanon, Delphine, additional, Knöfelv, Christina, additional, Llewellyn, Philip L, additional, and Férey, Gérard, additional

Published
2009
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192. Structural Transitions and Flexibility during Dehydration−Rehydration Process in the MOF-type Aluminum Pyromellitate Al2(OH)2[C10O8H2] (MIL-118)

Author

Volkringer, Christophe, primary, Loiseau, Thierry, additional, Guillou, Nathalie, additional, Férey, Gérard, additional, Haouas, Mohamed, additional, Taulelle, Francis, additional, Audebrand, Nathalie, additional, Margiolaki, Irene, additional, Popov, Dmitry, additional, Burghammer, Manfred, additional, and Riekel, Christian, additional

Published
2009
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198. Combined NMR, SAXS, and DLS Study of Concentrated Clear Solutions Used in Silicalite-1 Zeolite Synthesis

Author

Aerts, Alexander, primary, Follens, Lana R. A., additional, Haouas, Mohamed, additional, Caremans, Tom P., additional, Delsuc, Marc-André, additional, Loppinet, Benoit, additional, Vermant, Jan, additional, Goderis, Bart, additional, Taulelle, Francis, additional, Martens, Johan A., additional, and Kirschhock, Christine E. A., additional

Published
2007
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200. Tunable Keplerate Type-Cluster 'Mo132' Cavity with Dicarboxylate Anions.

Author

Lai, Thanh ‐ Loan, Awada, Mouhamad, Floquet, Sébastien, Roch ‐ Marchal, Catherine, Watfa, Nancy, Marrot, Jérôme, Haouas, Mohamed, Taulelle, Francis, and Cadot, Emmanuel

Subjects
CARBOXYLATES, ANIONS, LIGAND exchange reactions, SUCCINATES, METHYLAMMONIUM, NUCLEAR magnetic resonance, X-ray diffraction
Abstract

The internal functionalization of the Keplerate-type capsule Mo132 has been carried out by ligand exchange leading to the formation of glutarate and succinate containing species isolated as ammonium or dimethylammonium salts. Solution NMR analysis is consistent with asymmetric inner dicarboxylate ions containing one carboxylato group grafted onto the inner side of the spheroidal inorganic shell while the second hangs toward the center of the cavity. Such a disposition has been confirmed by the single-crystal X-ray diffraction analysis of the glutarate containing {Mo132} species. A detailed NMR solution study of the ligand-exchange process allowed determining the binding constant KL of acetate (AcO−), succinate (HSucc−) or glutarate (HGlu−) ligands at the 30 inner coordinating sites, which vary such as K [ABSTRACT FROM AUTHOR]

Published
2015
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