Center for Molecular Modeling - C. Kirschhock

How water and ion mobility affect the NMR fingerprints of the hydrated JBW zeolite: a combined computational-experimental investigation

alexander — Wed, 24 Aug 2022 07:27:54 +0000

S. Vanlommel, A.E.J. Hoffman, S. Smet, S. Radhakrishnan, K. Asselman, C. V. Chandran, E. Breynaert, C. Kirschhock, J.A. Martens, V. Van Speybroeck

Chemistry - A European Journal

28, 68, e202202621

2022

Abstract

An important aspect within zeolite synthesis is to make fully tunable framework materials with controlled aluminium distribution. A major challenge in characterising these zeolites at operating conditions is the presence of water. In this work, we investigate the effect of hydration on the 27 Al NMR parameters of the ultracrystalline K,Na-compensated aluminosilicate JBW zeolite using experimental and computational techniques. The JBW framework, with Si/Al ratio of 1, is an ideal benchmark system as a stepping stone towards more complicated zeolites. The presence and mobility of water and extraframework species directly affect NMR fingerprints. Excellent agreement between theoretical and experimental spectra is obtained provided dynamic methods are employed with hydrated structural models. This work shows how NMR is instrumental in characterising aluminium distributions in zeolites at operating conditions.

Gold Open Access

DOI

https://doi.org/10.1002/chem.202202621

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Chemistry A European J - 2022 - Vanlommel - How Water and Ion Mobility Affect the NMR Fingerprints of the Hydrated JBW.pdf

Super-ions of sodium cations with hydrated hydroxide anions: inorganic structure-directing agents in zeolite synthesis

leen — Tue, 15 Feb 2022 09:52:42 +0000

K. Asselman, N. Pellens, S. Radhakrishnan, C. V. Chandran, J.A. Martens, F. Taulelle, T. Verstraelen, M. Hellstrom, E. Breynaert, C. Kirschhock

Materials Horizons

Volume 8, Issue 9, Pages 2576-2583

2021

Abstract

In inorganic zeolite formation, a direct correspondence between liquid state species in the synthesis and the supramolecular decoration of the pores in the as-made final zeolite has never been reported. In this paper, a direct link between the sodium speciation in the synthesis mixture and the pore structure and content of the final zeolite is demonstrated in the example of hydroxysodalite. Super-ions with 4 sodium cations bound by mono- and bihydrated hydroxide are identified as structure-directing agents for the formation of this zeolite. This documentation of inorganic solution species acting as a templating agent in zeolite formation opens new horizons for zeolite synthesis by design.

DOI

http://dx.doi.org/10.1039/d1mh00733e

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d1mh00733e.pdf

Chlorination of a Zeolitic-Imidazolate Framework Tunes Packing and van der Waals Interaction of Carbon Dioxide for Optimized Adsorptive Separation

sven — Sun, 07 Feb 2021 12:54:58 +0000

L.H. Wee, S. Vandenbrande, S.M.J. Rogge, J. Wieme, K. Asselman, E. Jardim, J. Silvestre-Albero, J. Navarro, V. Van Speybroeck, J.A. Martens, C. Kirschhock

JACS (Journal of the American Chemical Society)

143 (13), 4962-4968

2021

Abstract

Molecular separation of carbon dioxide (CO₂) and methane (CH₄) is of growing interest for biogas upgrading, carbon capture and utilization, methane synthesis and for purification of natural gas. Here, we report a new zeolitic-imidazolate framework (ZIF), coined COK-17, with exceptionally high affinity for the adsorption of CO₂ by London dispersion forces, mediated by chlorine substituents of the imidazolate linkers. COK-17 is a new type of flexible zeolitic-imidazolate framework Zn(4,5-dichloroimidazolate)₂ with the SOD framework topology. Below 200 K it displays a metastable closed-pore phase next to its stable open-pore phase. At temperatures above 200 K, COK-17 always adopts its open-pore structure, providing unique adsorption sites for selective CO₂ adsorption and packing through van der Waals interactions with the chlorine groups, lining the walls of the micropores. Localization of the adsorbed CO₂ molecules by Rietveld refinement of X-ray diffraction data and periodic density functional theory calculations revealed the presence and nature of different adsorption sites. In agreement with experimental data, grand canonical Monte Carlo simulations of adsorption isotherms of CO₂ and CH₄ in COK-17 confirmed the role of the chlorine functions of the linkers and demonstrated the superiority of COK-17 compared to other adsorbents such as ZIF-8 and ZIF-71.

Gold Open Access

DOI

http://dx.doi.org/10.1021/jacs.0c08942

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jacs.0c08942.pdf

Alternating Copolymer of Double Four Ring Silicate and Dimethyl Silicone Monomer - PSS-1

steven — Mon, 29 May 2017 10:03:44 +0000

S. Smet, S. Vandenbrande, P. Verlooy, S. Kerkhofs, E. Breynaert, C. Kirschhock, C. Martineau, F. Taulelle, V. Van Speybroeck, J.A. Martens

Chemistry - A European Journal

23 (47), 11286-11293

2017

Abstract

A new copolymer consisting of double four ring (D4R) silicate units linked by dimethylsilicone monomer referred to as polyoligosiloxysilicone number one (PSS-1) was synthesized. The D4R building unit is provided by hexamethyleneimine cyclosilicate hydrate crystals, which were dehydrated and reacted with dichlorodimethylsilane. The local structure of D4R silicate units and dimethyl silicone monomers was revealed by multidimensional solid-state NMR, FTIR and modeling. On average, D4R silicate units have 6.8 silicone linkages. Evidence for preferential unidirectional growth and chain ordering within the PSS-1 copolymer was provided by STEM and TEM. The structure of PSS-1 copolymer consists of twisted columns of D4R silicate units with or without cross-linking. Both models are consistent with the spectroscopic, microscopic and physical properties. PSS-1 chains are predicted to be mechanically strong compared to silicones such as PDMS, yet more flexible than rigid silica materials such as zeolites.

DOI

http://dx.doi.org/10.1002/chem.201701237

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Smet_et_al-2017-Chemistry_-_A_European_Journal.pdf

A Flexible Photoactive Titanium Metal-Organic Framework Based on a [Ti-3(IV)(mu(3)-O)(O)(2)(COO)(6)] Cluster

michel — Fri, 21 Aug 2015 19:59:38 +0000

B. Bueken, F. Vermoortele, D.E.P. Vanpoucke, H. Reinsch, C. Tsou, P. Valvekens, T. De Baerdemaeker, R. Ameloot, C. Kirschhock, V. Van Speybroeck, J. Mayer, D. De Vos

Angewandte Chemie int. Ed.

127, 14118 –14123

2015

Abstract

The synthesis of titanium-carboxylate metal-organic frameworks (MOFs) is hampered by the high reactivity of the commonly employed alkoxide precursors. Herein, we present an innovative approach to titanium-based MOFs by the use of titanocene dichloride to synthesize COK-69, the first breathing Ti MOF, which is built up from trans-1,4-cyclo-hexanedicarboxylate linkers and an unprecedented [Ti-3(IV)(mu(3)-O)(O)(2)(COO)(6)] cluster. The photoactive properties of COK-69 were investigated in depth by proton-coupled electron-transfer experiments, which revealed that up to one Ti-IV center per cluster can be photoreduced to Ti-III while preserving the structural integrity of the framework. The electronic structure of COK-69 was determined by molecular modeling, and a band gap of 3.77 eV was found.

DOI

http://dx.doi.org/10.1002/anie.201505512

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Bueken_et_al-2015-Angewandte_Chemie.pdf

Flexibility versus rigidity: what determines the stability of zeolite frameworks? A case study

michel — Tue, 29 Apr 2014 19:07:20 +0000

E. Verheyen, L. Joos, C. Martineau, C.J. Dawson, C. Weidenthaler, W. Schmidt, R. Yuan, E. Breynaerts, V. Van Speybroeck, M. Waroquier, F. Taulelle, M.M.J. Treacy, J.A. Martens, C. Kirschhock

Materials Horizons

Vol. 1 , 582 - 587

2014

Abstract

All silica COK-14/-COK-14 with OKO topology is the first case of a zeolite which reversibly transforms from a systematically interrupted to a fully connected state and back. Analysis of the opening/closing behavior allowed the study of entropy and framework flexibility as determinants for the stability of zeolite topologies, which, until now, has been experimentally inaccessible. Interconversion of the all-silica COK-14 zeolite with fully connected OKO topology and its -COK-14 variant with systematic framework interruption was investigated using high-temperature XRD, thermogravimetric analysis, Si-29 MAS NMR, nitrogen adsorption and a range of modelling techniques. Specific framework bonds in the OKO framework can be reversibly hydrolyzed and condensed. Structural silanols of the parent -COK-14, prepared by degermanation of the IM-12 zeolite, were condensed by heating at 923 K, and hydrolyzed again to the initial state by contacting the zeolite with warm water. Molecular modelling revealed an inversion of the relative stabilities for both variants depending on temperature and hydration. Condensation of the structural silanols in -COK-14 to COK-14 is entropy driven, mainly resulting from the release of water molecules. Framework reopening in the presence of water is spontaneous due to the high rigidity of the fully connected OKO framework. Isomorphous substitution was demonstrated as a viable option for stabilization of the fully connected OKO framework as this renders the closed framework flexible.

DOI

http://dr.doi.org/10.1039/c4mh00127c

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manuscript mat Hor.pdf

Synthesis modulation as a tool to increase the catalytic activity of MOFs: the unique case of UiO-66(Zr)

michel — Sat, 18 May 2013 19:26:34 +0000

F. Vermoortele, B. Bueken, G. Le Bars, B. Van de Voorde, M. Vandichel, K. Houthoofd, A. Vimont, M. Daturi, M. Waroquier, V. Van Speybroeck, C. Kirschhock, D. De Vos

JACS (Journal of the American Chemical Society)

135 (31), 11465–11468

2013

Abstract

The catalytic activity of the zirconium terephthalate UiO-66(Zr) can be drastically increased by using a modulation approach. The combined use of trifluoroacetic acid and HCl during the synthesis results in a highly crystalline material, with partial substitution of terephthalates by trifluoroacetate. Thermal activation of the material leads not only to dehydroxylation of the hexanuclear Zr cluster but also to post-synthetic removal of the trifluoroacetate groups, resulting in a more open framework with a large number of open sites. Consequently, the material is a highly active catalyst for several Lewis acid catalyzed reactions.

DOI

http://dx.doi.org/10.1021/ja405078u

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13_jacs_135_11465_Vermoortele.pdf

Entropy-Driven Chemisorption of NOx on Phosphotungstic Acid

michel — Fri, 17 Aug 2012 06:49:36 +0000

S. Heylen, L. Joos, V. Van Speybroeck, C. Kirschhock, J.A. Martens

Angewandte Chemie int. Ed.

51 (44), 11010-11013

2012

Abstract

Nitrogen oxides, NOx, are formed in combustion engines. They contribute to acid rain and the formation of ozone and are hazardous for men and environment. In this article, a process was investigated that can 'capture' the NOx from the exhaust gases using heteropoly acids and can later release them for processing. One of the main conclusions is that the mobility of the captured and released molecules is the key to control the reaction. This can now be used to optimize and commercialize the technology.

Stikstofoxiden, aangeduid als NOx, worden gevormd in verbrandingsmotoren. Ze dragen bij tot zure regen, de vorming van ozon en zijn dus schadelijk voor mens en milieu. In dit artikel werd een proces onderzocht dat de NOx kan ‘vangen’ uit de uitlaatgassen aan de hand van heteropolyzuren en later terug kan vrijgeven voor verdere verwerking. Een van de belangrijkste vaststellingen is dat de mobiliteit van de opgeslagen en vrijgegeven moleculen de sleutel is voor het controleren van het proces. De conclusies van het onderzoek kunnen nu verder gebruikt worden voor de optimalisering en commercialisering van het proces.

http://www.ugent.be/nl/actueel/nieuws/persberichten/stikstofoxide-nox-ve...

NOx adsorption on Phosphotungstic acid is entropy-driven due to the watermolecules that are released.

DOI

http://dx.doi.org/10.1002/ange.201205636

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12 angewandte chem 51(44)11010 Heylen.pdf

Multi-level Modeling of Silica–Template Interactions During Initial Stages of Zeolite Synthesis

wim — Mon, 03 Oct 2011 12:14:17 +0000

T. Verstraelen, B.M. Szyja, D. Lesthaeghe, R. Declerck, V. Van Speybroeck, M. Waroquier, A.P.J. Jansen, A. Aerts, L.R.A Follens, J.A. Martens, C. Kirschhock, R.A. van Santen

Topics in Catalysis

52 (9), 1261-1271

2009

Abstract

Zeolite synthesis is driven by structure-directing agents, such as tetrapropyl ammonium ions (TPA(+)) for Silicalite-1 and ZSM-5. However, the guiding role of these organic templates in the complex assembly to highly ordered frameworks remains unclear, limiting the prospects for advanced material synthesis. In this work, both static ab initio and dynamic classical modeling techniques are employed to provide insight into the interactions between TPA(+) and Silicalite-1 precursors. We find that as soon as the typical straight 10-ring channel of Silicalite-1 or ZSM-5 is formed from smaller oligomers, the TPA(+) template is partially squeezed out of the resulting cavity. Partial retention of the template in the cavity is, however, indispensable to prevent collapse of the channel and subsequent hydrolysis.

DOI

http://dx.doi.org/10.1007/s11244-009-9275-4

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09 topics cat 52(9)1261 verstraelen.pdf

MFI Fingerprint: How Pentasil-Induced IR Bands Shift during Zeolite Nanogrowth

wim — Mon, 03 Oct 2011 08:53:14 +0000

D. Lesthaeghe, P. Vansteenkiste, T. Verstraelen, A. Ghysels, C. Kirschhock, J.A. Martens, V. Van Speybroeck, M. Waroquier

Journal of Physical Chemistry C

112 (25), 9186-9191

2008

Abstract

Silicalite-1 zeolite exhibits a characteristic pentasil framework vibration around 540−550 cm−1. In the initial stages of zeolite synthesis, however, this band is observed at much higher wavenumbers: literature shows this vibration to depend on particle size and to shift over 100 cm−1 with increasing condensation. In this work, the pentasil vibration frequency was derived from theoretical molecular dynamics simulations to obtain the correct IR band assignments for important nanoparticles. The IR spectroscopic fingerprint of oligomeric five-ring containing precursors proposed in the literature was computed and compared with experimental data. Our theoretical results show that, while isolated five-membered rings show characteristic vibrational bands around 650 cm−1, the combination of five-membered rings in the full MFI-type structure readily generates the bathochromic shift to the typical pentasil vibration around 550 cm−1. As opposed to what was previously believed, the IR band does not shift gradually as nanoparticle size increases, but it is highly dependent on the specific way structural units are added. The most important feature is the appearance of an additional band when double five-membered rings are included, which allows for a clear distinction between the key stages of early zeolite nucleation. Furthermore, the combination of the simulated spectra with the experimental observation of this spectral feature in nanoparticles extracted from silicalite-1 clear solutions supports their structured nature. The theoretical insights on the dependency of pentasil vibrations with the degree of condensation offer valuable support toward future investigations on the genesis of a zeolite crystal.

DOI

http://dx.doi.org/10.1021/jp711550s

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08 j. phys. chem. C 112(25)9186 lesthaeghe.pdf