Center for Molecular Modeling - E.J. Meijer

Dynamic interplay between defective UiO-66 and protic solvents in activated processes

chiara — Fri, 23 Aug 2019 13:17:09 +0000

C. Caratelli, J. Hajek, E.J. Meijer, M. Waroquier, V. Van Speybroeck

Chemistry - A European Journal

25 (67), 15315-15325

2019

Abstract

UiO‐66, composed by Zr‐oxide inorganic bricks [Zr6(μ3‐O)4(μ3‐OH)4] and organic terephthalate linkers, is one of the most studied metal–organic frameworks (MOFs) due to its exceptional thermal, chemical, and mechanical stability. Thanks to its high connectivity, the material can withstand structural deformations during activation processes such as linker exchange, dehydration, and defect formation. These processes do alter the zirconium coordination number in a dynamic way, creating open metal sites for catalysis and thus are able to tune the catalytic properties. In this work, it is shown, by means of first‐principle molecular‐dynamics simulations at operating conditions, how protic solvents may facilitate such changes in the metal coordination. Solvent can induce structural rearrangements in the material that can lead to undercoordinated but also overcoordinated metal sites. This is demonstrated by simulating activation processes along well‐chosen collective variables. Such enhanced MD simulations are able to track the intrinsic dynamics of the framework at realistic conditions.

DOI

http://dx.doi.org/10.1002/chem.201903178

Influence of a confined methanol solvent on the reactivity of active sites in UiO-66

chiara — Thu, 12 Oct 2017 13:59:10 +0000

C. Caratelli, J. Hajek, S.M.J. Rogge, S. Vandenbrande, E.J. Meijer, M. Waroquier, V. Van Speybroeck

ChemPhysChem

19 (4), 420-429

2018

Abstract

UiO-66, composed of Zr-oxide bricks and terephthalate linkers, is currently one of the most studied metal-organic frameworks due to its exceptional stability. Defects can be introduced in the structure, creating undercoordinated Zr atoms which are Lewis acid sites. Here, additional Brønsted sites can be generated by coordinated protic species from the solvent. In this contribution, a multilevel modeling approach was applied to unravel the effect of a confined methanol solvent on the active sites in UiO-66. First, active sites were explored with static periodic density functional theory calculations to investigate adsorption of water and methanol. Solvent was then introduced in the pores with grand canonical Monte Carlo simulations, followed by a series of molecular dynamics simulations at operating conditions. A hydrogen-bonded network of methanol molecules is formed, allowing the protons to shuttle between solvent methanol, adsorbed water, and the inorganic brick. Upon deprotonation of an active site, the methanol solvent aids the transfer of protons and stabilizes charged configurations via hydrogen bonding, which could be crucial in stabilizing reactive intermediates. The multilevel modeling approach adopted here sheds light on the important role of a confined solvent on the active sites in the UiO-66 material, introducing dynamic acidity in the system at finite temperatures by which protons may be easily shuttled from various positions at the active sites.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1002/cphc.201701109

Private attachment

Caratelli_et_al-2018-ChemPhysChem.pdf

Acidity constant (pKa) calculation of large solvated dye molecules: evaluation of two advanced molecular dynamics methods

michel — Sat, 09 Jul 2016 19:46:50 +0000

T. De Meyer, B. Ensing, S.M.J. Rogge, K. De Clerck, E.J. Meijer, V. Van Speybroeck

ChemPhysChem

17 (21), 3447–3459

2016

Abstract

pH-sensitive dyes are increasingly applied onto polymer substrates for the creation of novel sensor materials. Recently, these dye molecules have been modified to form a covalent bond with the polymer host. This can have a large influence on the pH-sensitive properties, in particular on the acidity constant (pKa). Obtaining molecular control over the factors that influence the pK$_a$ value is mandatory for future intelligent design of sensor materials. Herein, we show that advanced molecular dynamics (MD) methods have reached the level where pKa values of large solvated dye molecules can be predicted with high accuracy. Two MD methods are used in this work: steered or restrained MD and the insertion/deletion scheme. Both are first calibrated on a set of phenol derivatives and afterwards applied to the dye molecule Bromothymol Blue. Excellent agreement with experimental values is obtained, which opens perspectives for using these methods for designing dye molecules.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1002/cphc.201600734

Private attachment

Meyer_et_al-2016-ChemPhysChem.pdf

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

kristof — Thu, 04 Jun 2015 13:20:59 +0000

K. De Wispelaere, C.S. Wondergem, B. Ensing, K. Hemelsoet, E.J. Meijer, B.M. Weckhuysen, V. Van Speybroeck, J. Ruiz-Martinez

ACS Catalysis

6, 1991-2002

2016

Abstract

The role of water in the methanol-to-olefins (MTO) process over H-SAPO-34 has been elucidated by a combined theoretical and experimental approach, encompassing advanced molecular dynamics simulations and in-situ micro-spectroscopy. First principle calculations at the molecular level point out that water competes with methanol and propene for direct access to the Brønsted acid sites. This results in less efficient activation of these molecules, which are crucial for the formation of the hydrocarbon pool. Furthermore, lower intrinsic methanol reactivity towards methoxide formation has been observed. These observations are in line with a longer induction period observed from in-situ UV-Vis micro-spectroscopy experiments. These experiments revealed a slower and more homogeneous discoloration of H-SAPO-34, while in-situ confocal fluorescence microscopy confirmed the more homogeneous distribution and larger amount of MTO intermediates when co-feeding water. As such it is show that water induces a more efficient use of the H-SAPO-34 catalyst crystals at the microscopic level. The combined experimental theoretical approach gives a profound insight into the role of water on the catalytic process at the molecular and single particle level.

DOI

http://dx.doi.org/10.1021/acscatal.5b02139

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acscatal%2E5b02139.pdf

Complex reaction environments and competing reaction mechanisms in zeolite catalysis: insights from advanced molecular dynamics

kristof — Fri, 31 Oct 2014 14:33:45 +0000

K. De Wispelaere, B. Ensing, A. Ghysels, E.J. Meijer, V. Van Speybroeck

Chemistry - A European Journal

21 (26), 9385-9396

2015

Abstract

The methanol to olefins process is a show case example of complex zeolite-catalyzed chemistry. At real operating conditions, many factors such as framework flexibility, adsorption of various guest molecules and competitive reaction pathways, affect reactivity. In this paper we show the strength of first principle molecular dynamics techniques to capture this complexity by means of two case studies. Firstly, the adsorption behavior of methanol and water in H-SAPO-34 at 350 °C is investigated. Hereby we observed an important degree of framework flexibility and proton mobility. Secondly, we studied the methylation of benzene by methanol via a competitive direct and stepwise pathway in the AFI topology. Both case studies clearly show that a first principle molecular dynamics approach enables to obtain unprecedented insights into zeolite-catalyzed reactions at the nanometer scale.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1002/chem.201500473

Private attachment

15_ChemEurJ_xxxx_De_Wispelaere.pdf

De-Wispelaere_et_al-2015-Chemistry_-_A_European_Journal.pdf

Investigating the outstanding dynamic behavior of protons on UiO-66 defective sites

chiara — Mon, 29 Jan 2018 09:15:33 +0000

C. Caratelli, A. Tiwari, M. Waroquier, B. Ensing, E.J. Meijer, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

EuroMOF 2017

Delft, The Netherlands

Sunday, 29 October, 2017 to Wednesday, 1 November, 2017

Influence of a confined methanol solvent on the reactivity of active sites in UiO-66

chiara — Mon, 29 Jan 2018 09:02:40 +0000

C. Caratelli, J. Hajek, S.M.J. Rogge, S. Vandenbrande, E.J. Meijer, M. Waroquier, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

NCCC XIX

Noordwijkerhout,The Netherlands

Monday, 5 March, 2018 to Wednesday, 7 March, 2018

pKa calculations based on advanced MD simulations

thierry — Thu, 24 Dec 2015 15:48:08 +0000

T. De Meyer, B. Ensing, K. Hemelsoet, K. De Clerck, V. Van Speybroeck, E.J. Meijer

ISBN/ISSN:

Poster

Conference / event / venue

CHAINS 2015

Veldhoven, Amsterdam

Tuesday, 1 December, 2015 to Wednesday, 2 December, 2015

pKa calculations based on advanced MD simulations

thierry — Tue, 17 Nov 2015 09:52:46 +0000

T. De Meyer, B. Ensing, K. Hemelsoet, K. De Clerck, V. Van Speybroeck, E.J. Meijer

ISBN/ISSN:

Poster

Conference / event / venue

Holland Research School of Molecular Chemistry Symposium 2015

Vrije Universiteit, Amsterdam, The Netherlands

Thursday, 5 November, 2015

Exploring New Frontiers in Modeling Complex Zeolite-Catalyzed Reactions Using Advanced Molecular Dynamics Techniques

kristof — Mon, 16 Feb 2015 10:49:40 +0000

K. De Wispelaere, B. Ensing, A. Ghysels, E.J. Meijer, V. Van Speybroeck

O-Th-408-13

ISBN/ISSN:

Talk

Conference / event / venue

24th North American Catalysis Society Meeting (NAM24)

Pittsburgh, PA, USA

Sunday, 14 June, 2015 to Friday, 19 June, 2015

Abstract (private)

Abstract_NAM24_KDW.pdf

Abstract

Paper_12530_extendedabstract_3413_0.pdf

Conference reference

NAM24