Center for Molecular Modeling - F. Vermoortele

A breathing zirconium metal-organic framework with reversible loss of crystallinity by correlated nanodomain formation

jelle — Tue, 02 Feb 2016 07:37:01 +0000

B. Bueken, F. Vermoortele, M.J. Cliffe, M.T. Wharmby, D. Foucher, J. Wieme, L. Vanduyfhuys, C. Martineau, N. Stock, F. Taulelle, V. Van Speybroeck, A.L. Goodwin, D. De Vos

Chemistry - A European Journal

2016, 22, 1-5

2016

Abstract

The isoreticular analogue of the metal–organic framework UiO-66(Zr), synthesized with the flexible trans-1,4-cyclohexanedicarboxylic acid as linker, shows a peculiar breathing behavior by reversibly losing long-range crystalline order upon evacuation. The underlying flexibility is attributed to a concerted conformational contraction of up to two thirds of the linkers, which breaks the local lattice symmetry. X-ray scattering data are described well by a nanodomain model in which differently oriented tetragonal-type distortions propagate over about 7–10 unit cells.

DOI

http://dx.doi.org/10.1002/chem.201600330

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chem.201600330 Bart Bueken Zrcdc.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

Active site engineering in UiO-66 type metal-organic frameworks by intentional creation of defects: a theoretical rationalization

mat — Tue, 30 Sep 2014 15:08:29 +0000

M. Vandichel, J. Hajek, F. Vermoortele, D. De Vos, M. Waroquier, V. Van Speybroeck

CrystEngComm

17 (2), 395-406

2015

Abstract

The catalytic activity of the Zr-benzenedicarboxylate (Zr-BDC) UiO-66 can be drastically increased in the absence of part of the linkers, as it removes the full coordination of the framework metal ions and leads to open sites. As a result, metal centers become more accessible and thus more active for Lewis acid catalysed reactions. Addition of modulators (MDL) to the synthesis mixture can create more linker deficiencies (Vermoortele et al., J Am Chem Soc, 2013, 135, 11465) and can lead to a significant increase of the catalytic activity due to the creation of a larger number of open sites. In this paper, we rationalize the function of the modulators under real synthesis conditions by the construction of free energy diagrams. The UiO-66 type materials form a very appropriate test case as the effect of addition of modulators hydrochloric acid (HCl) and trifluoroacetate (TFA) has been intensively investigated experimentally for the synthesis process and post-synthetic thermal activation. In synthesis conditions, direct removal of BDC linkers requires a high free energy but replacement of such linker by one or more TFA species might occur especially at high TFA:BDC ratios in the reaction mixture. The presence of HCl furthermore enhances the creation of defect structures. Post-synthesis activation procedures at higher temperatures lead to a substantial removal of the species coordinated to the Zr bricks creating open metal sites. A mechanistic pathway is presented for the dehydroxylation process of the hexanuclear Zr cluster. For the citronellal cyclization, we show that the presence of some residual TFA in the structure may lead to faster reactions in complete agreement with experiment. Hirshfeld-e partial charges for the Zr ions have been computed to investigate their sensitivity to substituent effects; a strong correlation with the experimental Hammett parameters, and with the rates of the citronellal cyclization is found. The theoretical rationalization may serve as a basis for detailed active site engineering studies.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1039/C4CE01672F

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14_crystengcomm_xxxx_Vandichel.pdf

c4ce01672f1.pdf

Active site engineering in UiO-66 type Metal Organic Frameworks by intentional creation of defects : A theoretical rationalization

michel — Tue, 12 Aug 2014 19:16:17 +0000

M. Vandichel, J. Hajek, F. Vermoortele, M. Waroquier, D. De Vos, V. Van Speybroeck

CrystEngComm

First published online 15 Sep 2014

2014

Published while none of the authors were employed at the CMM

Abstract

The catalytic activity of the Zr-benzenedicarboxylate (Zr-BDC) UiO-66 can be drastically increased in the absence of part of the linkers, as it removes the full coordination of the framework metal ions and leads to open sites. As a result, metal centers become more accessible and thus more active for Lewis acid catalysed reactions. Addition of modulators (MDL) to the synthesis mixture can create more linker deficiencies (Vermoortele et al., J Am Chem Soc, 2013, 135, 11465) and can lead to a significant increase of the catalytic activity due to the creation of a larger number of open sites. In this paper, we rationalize the function of the modulators under real synthesis conditions by the construction of free energy diagrams. The UiO-66 type materials form a very appropriate test case as the effect of addition of modulators HCl and trifluoroacetate (TFA) has been intensively investigated experimentally for the synthesis process and post-synthetic thermal activation. In synthesis conditions, direct removal of BDC linkers requires a high free energy but replacement of such linker by one or more TFA species might occur especially at high TFA:BDC ratios in the reaction mixture. The presence of HCl furthermore enhances the creation of defect structures. Post-synthesis activation procedures at higher temperatures lead to a substantial removal of the species coordinated to the Zr bricks creating open metal sites. A mechanistic pathway is presented for the dehydroxylation process of the hexanuclear Zr cluster. For the citronellal cyclization, we show that the presence of some residual TFA in the structure may lead to faster reactions in complete agreement with experiment. Hirshfeld-e partial charges for the Zr ions have been computed to investigate their sensitivity to substituent effects; a strong correlation with the experimental Hammett parameters, and with the rates of the citronellal cyclization is found. The theoretical rationalization may serve as a basis for detailed active site engineering studies.

DOI

http://dx.doi.org/10.1039/C4CE01672F

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

Insight in the activity and diastereoselectivity of various Lewis acid catalysts for the citronellal cyclization

mat — Wed, 13 Feb 2013 12:38:41 +0000

M. Vandichel, F. Vermoortele, S. Cottenie, D. De Vos, M. Waroquier, V. Van Speybroeck

Journal of Catalysis

305, 118-129

2013

Abstract

Industrial (-)-menthol production generally relies on the hydrogenation of (-)-isopulegol, which is in turn produced with high selectivity by cyclization of (+)-citronellal. This paper uses a combined theoretical and experimental approach to study the activity and selectivity of three Lewis acid catalysts for this reaction, namely ZnBr2, aluminum tris(2,6-diphenylphenoxide) (ATPH) and the heterogeneous metal-organic framework Cu3BTC2 (BTC = benzene-1,3,5-tricarboxylate). ATPH is a strong Lewis acid homogeneous catalyst with bulky ligands which provides very high selectivities for the desired stereo-isomer (> 99 %). The performance of the catalysts was evaluated as a function of temperature, which revealed that higher catalyst activity allows working at lower temperatures and improves the selectivity for isopulegol. The selectivity distribution is kinetically driven for ZnBr2 and ATPH. The theoretical selectivity distributions rely on the determination of an extensive set of diastereomeric transition states, for which the differences in free energy have been calculated using a complementary set of ab initio techniques. Given the sensitivity of the selectivity to small Gibbs free energy differences, the agreement between experimental and theoretical selectivities is satisfactory. On basis of the obtained insights rational design of new catalysts may be obtained. As proof of concept, the hypothetical Cu3(BTC-(NO2)3)2 Lewis catalyst – in which each phenyl hydrogen of the BTC ligand is replaced by a nitro group - is predicted to be very selective.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1016/j.jcat.2013.04.017

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Vandichel-JC-2013-ActivitySelectivityLewisAcidCatalystsForCitronellalCyclization.pdf

13_jcatlysis_305_118_vandichel.pdf

Electronic effects of linker substitution on Lewis acid catalysis with Metal-organic frameworks

michel — Wed, 30 Nov 2011 14:44:33 +0000

F. Vermoortele, M. Vandichel, B. Van de Voorde, R. Ameloot, M. Waroquier, V. Van Speybroeck, D. De Vos

Angewandte Chemie int. Ed.

51(20), 4887-4890

2012

Abstract

Functionalized linkers can greatly increase the activity of metal–organic framework (MOF) catalysts with coordinatively unsaturated sites. A clear linear free-energy relationship (LFER) was found between Hammett σm values of the linker substituents X and the rate kX of a carbonyl-ene reaction. This is the first LFER ever observed for MOF catalysts. A 56-fold increase in rate was found when the substituent is a nitro group.

DOI

http://dx.doi.org/10.1002/anie.201108565

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12 angewandte chem int ed 51(20)4887 Vermoortele.pdf

Flexible Ti- and Zr-MOFs based on 1,4-trans-cyclohexanedicarboxylate linkers

samuel — Wed, 05 Feb 2020 13:59:00 +0000

B. Bueken, F. Vermoortele, H. Reinsch, M. Cliffe, M. Wharmby, C. Tsou, D.E.P. Vanpoucke, R. Ameloot, V. Van Speybroeck, A. Goodwin, F. Taulelle, J. Mayer, D. De Vos

ISBN/ISSN:0065-7727

Talk

Conference / event / venue

ACS' 251st National Meeting & Exposition

San Diego, CA, USA

Sunday, 13 March, 2016 to Thursday, 17 March, 2016

Conference reference

251st ACS National Meeting

Flexible Ti- and Zr-MOFs based on 1,4-trans-cyclohexaned icarb oxylate linkers

wim — Wed, 12 Aug 2015 07:09:26 +0000

B. Bueken, F. Vermoortele, H. Reinsch, M. Cliffe, M. Wharmby, C. Tsou, D.E.P. Vanpoucke, R. Ameloot, V. Van Speybroeck, F. Taulelle, A. Goodwin, J. Mayer, D. De Vos

ISBN/ISSN:

Poster

Conference / event / venue

EUROMOF2015

Potsdam am Templiner See (Berlin), Germany

Sunday, 11 October, 2015 to Wednesday, 14 October, 2015

Conference reference

EUROMOF2015

Insight in the activity of UiO-66-NH2 for the aldol condensation

julianna — Fri, 10 Apr 2015 08:11:20 +0000

J. Hajek, M. Vandichel, F. Vermoortele, M. Waroquier, D. De Vos, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

XVIth Netherlands' Catalysis and Chemistry Conference (NCCC XV)

Noordwijkerhout, The Netherlands

Monday, 2 March, 2015 to Wednesday, 4 March, 2015