Publications
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2014
Valvekens, P; Jonckheere, D; Baerdemaeker, T De; Kubarev, A V; Vandichel, M; Hemelsoet, K; Waroquier, M; Speybroeck, V Van; Smolders, E; Depla, D; Roeffaers, M B J; Vos, D De
In: CHEMICAL SCIENCE, vol. 5, no. 11, pp. 4517-4524, 2014, ISSN: 2041-6520.
@article{ISI:000343004300050,
title = {Base catalytic activity of alkaline earth MOFs: a (micro)spectroscopic
study of active site formation by the controlled transformation of
structural anions},
author = {P Valvekens and D Jonckheere and T De Baerdemaeker and A V Kubarev and M Vandichel and K Hemelsoet and M Waroquier and V Van Speybroeck and E Smolders and D Depla and M B J Roeffaers and D De Vos},
doi = {10.1039/c4sc01731e},
issn = {2041-6520},
year = {2014},
date = {2014-01-01},
journal = {CHEMICAL SCIENCE},
volume = {5},
number = {11},
pages = {4517-4524},
abstract = {A new method has been developed for generating highly dispersed base
sites on metal-organic framework (MOF) lattices. The base catalytic activity of two alkaline earth MOFs, M-2(BTC)(NO3)(DMF) (M = Ba or Sr},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
sites on metal-organic framework (MOF) lattices. The base catalytic activity of two alkaline earth MOFs, M-2(BTC)(NO3)(DMF) (M = Ba or Sr
Speybroeck, Veronique Van; Wispelaere, Kristof De; der Mynsbrugge, Jeroen Van; Vandichel, Matthias; Hemelsoet, Karen; Waroquier, Michel
First principle chemical kinetics in zeolites: the methanol-to-olefin process as a case study Journal Article
In: CHEMICAL SOCIETY REVIEWS, vol. 43, no. 21, pp. 7326-7357, 2014, ISSN: 0306-0012.
@article{ISI:000342908200006,
title = {First principle chemical kinetics in zeolites: the methanol-to-olefin
process as a case study},
author = {Veronique Van Speybroeck and Kristof De Wispelaere and Jeroen Van der Mynsbrugge and Matthias Vandichel and Karen Hemelsoet and Michel Waroquier},
doi = {10.1039/c4cs00146j},
issn = {0306-0012},
year = {2014},
date = {2014-01-01},
journal = {CHEMICAL SOCIETY REVIEWS},
volume = {43},
number = {21},
pages = {7326-7357},
abstract = {To optimally design next generation catalysts a thorough understanding
of the chemical phenomena at the molecular scale is a prerequisite.
Apart from qualitative knowledge on the reaction mechanism, it is also
essential to be able to predict accurate rate constants. Molecular
modeling has become a ubiquitous tool within the field of heterogeneous
catalysis. Herein, we review current computational procedures to
determine chemical kinetics from first principles, thus by using no
experimental input and by modeling the catalyst and reacting species at
the molecular level. Therefore, we use the methanol-to- olefin (MTO)
process as a case study to illustrate the various theoretical concepts.
This process is a showcase example where rational design of the catalyst
was for a long time performed on the basis of trial and error, due to
insufficient knowledge of the mechanism. For theoreticians the MTO
process is particularly challenging as the catalyst has an inherent
supramolecular nature, for which not only the Bronsted acidic site is
important but also organic species, trapped in the zeolite pores, must
be essentially present during active catalyst operation. All these
aspects give rise to specific challenges for theoretical modeling. It is
shown that present computational techniques have matured to a level
where accurate enthalpy barriers and rate constants can be predicted for
reactions occurring at a single active site. The comparison with
experimental data such as apparent kinetic data for well-defined
elementary reactions has become feasible as current computational
techniques also allow predicting adsorption enthalpies with reasonable
accuracy. Real catalysts are truly heterogeneous in a space-and
time-like manner. Future theory developments should focus on extending
our view towards phenomena occurring at longer length and time scales
and integrating information from various scales towards a unified
understanding of the catalyst. Within this respect molecular dynamics
methods complemented with additional techniques to simulate rare events
are now gradually making their entrance within zeolite catalysis. Recent
applications have already given a flavor of the benefit of such
techniques to simulate chemical reactions in complex molecular
environments.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
of the chemical phenomena at the molecular scale is a prerequisite.
Apart from qualitative knowledge on the reaction mechanism, it is also
essential to be able to predict accurate rate constants. Molecular
modeling has become a ubiquitous tool within the field of heterogeneous
catalysis. Herein, we review current computational procedures to
determine chemical kinetics from first principles, thus by using no
experimental input and by modeling the catalyst and reacting species at
the molecular level. Therefore, we use the methanol-to- olefin (MTO)
process as a case study to illustrate the various theoretical concepts.
This process is a showcase example where rational design of the catalyst
was for a long time performed on the basis of trial and error, due to
insufficient knowledge of the mechanism. For theoreticians the MTO
process is particularly challenging as the catalyst has an inherent
supramolecular nature, for which not only the Bronsted acidic site is
important but also organic species, trapped in the zeolite pores, must
be essentially present during active catalyst operation. All these
aspects give rise to specific challenges for theoretical modeling. It is
shown that present computational techniques have matured to a level
where accurate enthalpy barriers and rate constants can be predicted for
reactions occurring at a single active site. The comparison with
experimental data such as apparent kinetic data for well-defined
elementary reactions has become feasible as current computational
techniques also allow predicting adsorption enthalpies with reasonable
accuracy. Real catalysts are truly heterogeneous in a space-and
time-like manner. Future theory developments should focus on extending
our view towards phenomena occurring at longer length and time scales
and integrating information from various scales towards a unified
understanding of the catalyst. Within this respect molecular dynamics
methods complemented with additional techniques to simulate rare events
are now gradually making their entrance within zeolite catalysis. Recent
applications have already given a flavor of the benefit of such
techniques to simulate chemical reactions in complex molecular
environments.
der Voort, Pascal Van; Leus, Karen; Liu, Ying-Ya; Vandichel, Matthias; Speybroeck, Veronique Van; Waroquier, Michel; Biswas, Shyam
Vanadium metal-organic frameworks: structures and applications Journal Article
In: NEW JOURNAL OF CHEMISTRY, vol. 38, no. 5, pp. 1853-1867, 2014, ISSN: 1144-0546.
@article{ISI:000334832200006,
title = {Vanadium metal-organic frameworks: structures and applications},
author = {Pascal Van der Voort and Karen Leus and Ying-Ya Liu and Matthias Vandichel and Veronique Van Speybroeck and Michel Waroquier and Shyam Biswas},
doi = {10.1039/c3nj01130e},
issn = {1144-0546},
year = {2014},
date = {2014-01-01},
journal = {NEW JOURNAL OF CHEMISTRY},
volume = {38},
number = {5},
pages = {1853-1867},
abstract = {This perspective review paper describes the V-containing metal-organic
frameworks that have been developed since the first systematic reports
on MOFs almost 15 years ago. These hybrid crystalline materials,
containing V(III) or V(IV) as metal nodes, show interesting behavior in
oxidation catalysis and gas sorption. A significant amount of papers has
appeared on the use of these structures in gas (hydrocarbon, CO2)
separation. Promising future research and development of V-MOFs is
suggested.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
frameworks that have been developed since the first systematic reports
on MOFs almost 15 years ago. These hybrid crystalline materials,
containing V(III) or V(IV) as metal nodes, show interesting behavior in
oxidation catalysis and gas sorption. A significant amount of papers has
appeared on the use of these structures in gas (hydrocarbon, CO2)
separation. Promising future research and development of V-MOFs is
suggested.
Velazquez, Heriberto Diaz; Garcia, Yara Ruiz; Vandichel, Matthias; Madder, Annemieke; Verpoort, Francis
Water-soluble NHC-Cu catalysts: applications in click chemistry, bioconjugation and mechanistic analysis Journal Article
In: ORGANIC & BIOMOLECULAR CHEMISTRY, vol. 12, no. 46, pp. 9350-9356, 2014, ISSN: 1477-0520.
@article{ISI:000344989700010,
title = {Water-soluble NHC-Cu catalysts: applications in click chemistry,
bioconjugation and mechanistic analysis},
author = {Heriberto Diaz Velazquez and Yara Ruiz Garcia and Matthias Vandichel and Annemieke Madder and Francis Verpoort},
doi = {10.1039/c4ob01350f},
issn = {1477-0520},
year = {2014},
date = {2014-01-01},
journal = {ORGANIC & BIOMOLECULAR CHEMISTRY},
volume = {12},
number = {46},
pages = {9350-9356},
abstract = {Copper(I)-catalyzed 1,3-dipolar cycloaddition of azides and terminal
alkynes (CuAAC), better known as ``click'' reaction, has triggered the
use of 1,2,3-triazoles in bioconjugation, drug discovery, materials
science and combinatorial chemistry. Here we report a new series of
water-soluble catalysts based on N-heterocyclic carbene (NHC)-Cu
complexes which are additionally functionalized with a sulfonate group.
The complexes show superior activity towards CuAAC reactions and display
a high versatility, enabling the production of triazoles with different
substitution patterns. Additionally, successful application of these
complexes in bioconjugation using unprotected peptides acting as DNA
binding domains was achieved for the first time. Mechanistic insight
into the reaction mechanism is obtained by means of state-of-the-art
first principles calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
alkynes (CuAAC), better known as ``click'' reaction, has triggered the
use of 1,2,3-triazoles in bioconjugation, drug discovery, materials
science and combinatorial chemistry. Here we report a new series of
water-soluble catalysts based on N-heterocyclic carbene (NHC)-Cu
complexes which are additionally functionalized with a sulfonate group.
The complexes show superior activity towards CuAAC reactions and display
a high versatility, enabling the production of triazoles with different
substitution patterns. Additionally, successful application of these
complexes in bioconjugation using unprotected peptides acting as DNA
binding domains was achieved for the first time. Mechanistic insight
into the reaction mechanism is obtained by means of state-of-the-art
first principles calculations.
2013
Biswas, Shyam; Vanpoucke, Danny E P; Verstraelen, Toon; Vandichel, Matthias; Couck, Sarah; Leus, Karen; Liu, Ying-Ya; Waroquier, Michel; Speybroeck, Veronique Van; Denayer, Joeri F M; der Voort, Pascal Van
In: JOURNAL OF PHYSICAL CHEMISTRY C, vol. 117, no. 44, pp. 22784-22796, 2013, ISSN: 1932-7447.
@article{ISI:000326845400037,
title = {New Functionalized Metal-Organic Frameworks MIL-47-X (X = -Cl, -Br,
-CH3, -CF3, -OH, -OCH3): Synthesis, Characterization, and CO2 Adsorption
Properties},
author = {Shyam Biswas and Danny E P Vanpoucke and Toon Verstraelen and Matthias Vandichel and Sarah Couck and Karen Leus and Ying-Ya Liu and Michel Waroquier and Veronique Van Speybroeck and Joeri F M Denayer and Pascal Van der Voort},
doi = {10.1021/jp406835n},
issn = {1932-7447},
year = {2013},
date = {2013-11-01},
journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
volume = {117},
number = {44},
pages = {22784-22796},
abstract = {Six new functionalized vanadium hydroxo terephthalates [V-III(OH)(BDC-X)]center dot n(guests) (MIL-47(V-III)-X-AS) (BDC = 1,4-benzenedicarboxylate; X = -Cl, -Br, -CH3, -CF3, -OH, -OCH3; AS =
as-synthesized) along with the parent MIL-47 were synthesized under
rapid microwave-assisted hydrothermal conditions (170 degrees C, 30 min,
150 W). The unreacted H2BDC-X and/or occluded solvent molecules can be
removed by thermal activation under vacuum, leading to the empty-pore
forms of the title compounds (MIL-47(V-IV)-X). Except pristine MIL-47
(+III oxidation state), the vanadium atoms in all the evacuated
functionalized solids stayed in the +IV oxidation state. The phase
purity of the compounds was ascertained by X-ray powder diffraction
(XRPD), diffuse reflectance infrared Fourier transform (DRIFT)
spectroscopy, Raman, thermogravimetric (TG), and elemental analysis. The
structural similarity of the filled and empty-pore forms of the
functionalized compounds with the respective forms of parent MIL-47 was
verified by cell parameter determination from XRPD data. TGA and
temperature-dependent XRPD (TDXRPD) experiments in an air atmosphere
indicate high thermal stability in the 330-385 degrees C range. All the
thermally activated compounds exhibit significant microporosity (S-BET
in the 305-897 m(2) g(-1) range), as verified by the N-2 and CO2
sorption analysis. Among the six functionalized compounds,
MIL-47(V-IV)-OCH3 shows the highest CO2 uptake, demonstrating the
determining role of functional groups on the CO2 sorption behavior. For
this compound and pristine MIL-47(V-IV), Widom particle insertion
simulations were performed based on ab initio calculated crystal
structures. The theoretical Henry coefficients show a good agreement
with the experimental values, and calculated isosurfaces for the local
excess chemical potential indicate the enhanced CO2 affinity is due to
two effects: (i) the interaction between the methoxy group and CO2 and
(ii) the collapse of the MIL-47(V-IV)-OCH3 framework.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
as-synthesized) along with the parent MIL-47 were synthesized under
rapid microwave-assisted hydrothermal conditions (170 degrees C, 30 min,
150 W). The unreacted H2BDC-X and/or occluded solvent molecules can be
removed by thermal activation under vacuum, leading to the empty-pore
forms of the title compounds (MIL-47(V-IV)-X). Except pristine MIL-47
(+III oxidation state), the vanadium atoms in all the evacuated
functionalized solids stayed in the +IV oxidation state. The phase
purity of the compounds was ascertained by X-ray powder diffraction
(XRPD), diffuse reflectance infrared Fourier transform (DRIFT)
spectroscopy, Raman, thermogravimetric (TG), and elemental analysis. The
structural similarity of the filled and empty-pore forms of the
functionalized compounds with the respective forms of parent MIL-47 was
verified by cell parameter determination from XRPD data. TGA and
temperature-dependent XRPD (TDXRPD) experiments in an air atmosphere
indicate high thermal stability in the 330-385 degrees C range. All the
thermally activated compounds exhibit significant microporosity (S-BET
in the 305-897 m(2) g(-1) range), as verified by the N-2 and CO2
sorption analysis. Among the six functionalized compounds,
MIL-47(V-IV)-OCH3 shows the highest CO2 uptake, demonstrating the
determining role of functional groups on the CO2 sorption behavior. For
this compound and pristine MIL-47(V-IV), Widom particle insertion
simulations were performed based on ab initio calculated crystal
structures. The theoretical Henry coefficients show a good agreement
with the experimental values, and calculated isosurfaces for the local
excess chemical potential indicate the enhanced CO2 affinity is due to
two effects: (i) the interaction between the methoxy group and CO2 and
(ii) the collapse of the MIL-47(V-IV)-OCH3 framework.
Vandichel, Matthias; Vermoortele, Frederik; Cottenie, Stijn; Vos, Dirk E De; Waroquier, Michel; Speybroeck, Veronique Van
Insight in the activity and diastereoselectivity of various Lewis acid catalysts for the citronellal cyclization Journal Article
In: JOURNAL OF CATALYSIS, vol. 305, pp. 118-129, 2013, ISSN: 0021-9517.
@article{ISI:000322501000013,
title = {Insight in the activity and diastereoselectivity of various Lewis acid
catalysts for the citronellal cyclization},
author = {Matthias Vandichel and Frederik Vermoortele and Stijn Cottenie and Dirk E De Vos and Michel Waroquier and Veronique Van Speybroeck},
doi = {10.1016/j.jcat.2013.04.017},
issn = {0021-9517},
year = {2013},
date = {2013-09-01},
journal = {JOURNAL OF CATALYSIS},
volume = {305},
pages = {118-129},
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 stereoisomer (>99%). The performance
of the catalysts was evaluated as a function of temperature, which
revealed that a 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 Cu-3(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. (C) 2013 Elsevier Inc. All
rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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 stereoisomer (>99%). The performance
of the catalysts was evaluated as a function of temperature, which
revealed that a 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 Cu-3(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. (C) 2013 Elsevier Inc. All
rights reserved.
Vermoortele, Frederik; Bueken, Bart; Bars, Gaelle Le; de Voorde, Ben Van; Vandichel, Matthias; Houthoofd, Kristof; Vimont, Alexandre; Daturi, Marco; Waroquier, Michel; Speybroeck, Veronique Van; Kirschhock, Christine; Vos, Dirk E De
Synthesis Modulation as a Tool To Increase the Catalytic Activity of Metal-Organic Frameworks: The Unique Case of UiO-66(Zr) Journal Article
In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 135, no. 31, pp. 11465-11468, 2013, ISSN: 0002-7863.
@article{ISI:000323019400014,
title = {Synthesis Modulation as a Tool To Increase the Catalytic Activity of
Metal-Organic Frameworks: The Unique Case of UiO-66(Zr)},
author = {Frederik Vermoortele and Bart Bueken and Gaelle Le Bars and Ben Van de Voorde and Matthias Vandichel and Kristof Houthoofd and Alexandre Vimont and Marco Daturi and Michel Waroquier and Veronique Van Speybroeck and Christine Kirschhock and Dirk E De Vos},
doi = {10.1021/ja405078u},
issn = {0002-7863},
year = {2013},
date = {2013-08-01},
journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
volume = {135},
number = {31},
pages = {11465-11468},
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.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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.
Ghysels, An; Vanduyfhuys, Louis; Vandichel, Matthias; Waroquier, Michel; Speybroeck, Veronique Van; Smit, Berend
On the Thermodynamics of Framework Breathing: A Free Energy Model for Gas Adsorption in MIL-53 Journal Article
In: JOURNAL OF PHYSICAL CHEMISTRY C, vol. 117, no. 22, pp. 11540-11554, 2013, ISSN: 1932-7447.
@article{ISI:000320214800011,
title = {On the Thermodynamics of Framework Breathing: A Free Energy Model for
Gas Adsorption in MIL-53},
author = {An Ghysels and Louis Vanduyfhuys and Matthias Vandichel and Michel Waroquier and Veronique Van Speybroeck and Berend Smit},
doi = {10.1021/jp311601q},
issn = {1932-7447},
year = {2013},
date = {2013-06-01},
journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
volume = {117},
number = {22},
pages = {11540-11554},
abstract = {When adsorbing guest molecules, the porous metal-organic framework
MIL-53(Cr) may vary its cell parameters drastically while retaining its
crystallinity. A first approach to the thermodynamic analysis of this
``framework breathing'' consists of comparing the osmotic potential in
two distinct shapes only (large-pore and narrow-pore). In this paper, we
propose a generic parametrized free energy model including three
contributions: host free energy, guest-guest interactions, and
host-guest interaction. Free energy landscapes may now be constructed
scanning all shapes and any adsorbed amount of guest molecules. This
allows us to determine which shapes are the most stable states for
arbitrary combinations of experimental control parameters, such as the
adsorbing gas chemical potential, the external pressure, and the
temperature. The new model correctly reproduces the structural
transitions along the CO2 and CH4 isotherms. Moreover, our model
successfully explains the adsorption versus desorption hysteresis as a
consequence of the creation, stabilization, destabilization, and
disappearance of a second free energy minimum under the assumptions of a
first-order phase transition and collective behavior. Our general
thermodynamic description allows us to decouple the gas chemical
potential mu and mechanical pressure P as two independent thermodynamic
variables and predict the complete (mu, P) phase diagram for CO2
adsorption in MIL-53(Cr). The free energy model proposed here is an
important step toward a general thermodynamics description of flexible
metal-organic frameworks.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
MIL-53(Cr) may vary its cell parameters drastically while retaining its
crystallinity. A first approach to the thermodynamic analysis of this
``framework breathing'' consists of comparing the osmotic potential in
two distinct shapes only (large-pore and narrow-pore). In this paper, we
propose a generic parametrized free energy model including three
contributions: host free energy, guest-guest interactions, and
host-guest interaction. Free energy landscapes may now be constructed
scanning all shapes and any adsorbed amount of guest molecules. This
allows us to determine which shapes are the most stable states for
arbitrary combinations of experimental control parameters, such as the
adsorbing gas chemical potential, the external pressure, and the
temperature. The new model correctly reproduces the structural
transitions along the CO2 and CH4 isotherms. Moreover, our model
successfully explains the adsorption versus desorption hysteresis as a
consequence of the creation, stabilization, destabilization, and
disappearance of a second free energy minimum under the assumptions of a
first-order phase transition and collective behavior. Our general
thermodynamic description allows us to decouple the gas chemical
potential mu and mechanical pressure P as two independent thermodynamic
variables and predict the complete (mu, P) phase diagram for CO2
adsorption in MIL-53(Cr). The free energy model proposed here is an
important step toward a general thermodynamics description of flexible
metal-organic frameworks.
Liu, Ying-Ya; Couck, Sarah; Vandichel, Matthias; Grzywa, Maciej; Leus, Karen; Biswas, Shyam; Vollmer, Dirk; Gascon, Jorge; Kapteijn, Freek; Denayer, Joeri F M; Waroquier, Michel; Speybroeck, Veronique Van; der Voort, Pascal Van
New V-IV-Based Metal-Organic Framework Having Framework Flexibility and High CO2 Adsorption Capacity Journal Article
In: INORGANIC CHEMISTRY, vol. 52, no. 1, pp. 113-120, 2013, ISSN: 0020-1669.
@article{ISI:000313220500016,
title = {New V-IV-Based Metal-Organic Framework Having Framework Flexibility and
High CO2 Adsorption Capacity},
author = {Ying-Ya Liu and Sarah Couck and Matthias Vandichel and Maciej Grzywa and Karen Leus and Shyam Biswas and Dirk Vollmer and Jorge Gascon and Freek Kapteijn and Joeri F M Denayer and Michel Waroquier and Veronique Van Speybroeck and Pascal Van der Voort},
doi = {10.1021/ic301338a},
issn = {0020-1669},
year = {2013},
date = {2013-01-01},
journal = {INORGANIC CHEMISTRY},
volume = {52},
number = {1},
pages = {113-120},
abstract = {A vanadium based metal organic framework (MOF), VO(BPDC) (BPDC2- =
biphenyl-4,4'-dicarboxylate), adopting an expanded MIL-47 structure
type, has been synthesized via solvothermal and microwave methods. Its
structural and gas/vapor sorption properties have been studied. This
compound displays a distinct breathing effect toward certain adsorptives
at workable temperatures. The sorption isotherms of CO2 and CH4 indicate
a different sorption behavior at specific temperatures. In situ
synchrotron X-ray powder diffraction measurements and molecular
simulations have been utilized to characterize the structural
transition. The experimental measurements clearly suggest the existence
of both narrow pore and large pore forms. A free energy profile along
the pore angle was computationally determined for the empty host
framework. Apart from a regular large pore and a regular narrow pore
form, an overstretched narrow pore form has also been found.
Additionally, a variety of spectroscopic techniques combined with N-2
adsorption/desorption isotherms measured at 77 K demonstrate that the
existence of the mixed oxidation states V-III/V-IV in the titled MOF
structure compared to pure V-IV increases the difficulty in triggering
the flexibility of the framework.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
biphenyl-4,4'-dicarboxylate), adopting an expanded MIL-47 structure
type, has been synthesized via solvothermal and microwave methods. Its
structural and gas/vapor sorption properties have been studied. This
compound displays a distinct breathing effect toward certain adsorptives
at workable temperatures. The sorption isotherms of CO2 and CH4 indicate
a different sorption behavior at specific temperatures. In situ
synchrotron X-ray powder diffraction measurements and molecular
simulations have been utilized to characterize the structural
transition. The experimental measurements clearly suggest the existence
of both narrow pore and large pore forms. A free energy profile along
the pore angle was computationally determined for the empty host
framework. Apart from a regular large pore and a regular narrow pore
form, an overstretched narrow pore form has also been found.
Additionally, a variety of spectroscopic techniques combined with N-2
adsorption/desorption isotherms measured at 77 K demonstrate that the
existence of the mixed oxidation states V-III/V-IV in the titled MOF
structure compared to pure V-IV increases the difficulty in triggering
the flexibility of the framework.
2012
Vandichel, Matthias; Leus, Karen; der Voort, Pascal Van; Waroquier, Michel; Speybroeck, Veronique Van
Mechanistic insight into the cyclohexene epoxidation with VO(acac)(2) and tert-butyl hydroperoxide Journal Article
In: JOURNAL OF CATALYSIS, vol. 294, pp. 1-18, 2012, ISSN: 0021-9517.
@article{ISI:000309314500001,
title = {Mechanistic insight into the cyclohexene epoxidation with VO(acac)(2)
and tert-butyl hydroperoxide},
author = {Matthias Vandichel and Karen Leus and Pascal Van der Voort and Michel Waroquier and Veronique Van Speybroeck},
doi = {10.1016/j.jcat.2012.06.002},
issn = {0021-9517},
year = {2012},
date = {2012-10-01},
journal = {JOURNAL OF CATALYSIS},
volume = {294},
pages = {1-18},
abstract = {The epoxidation reaction of cyclohexene is investigated for the
catalytic system vanadyl acetylacetonate (VO(acac)(2)) with tert-butyl
hydroperoxide (TBHP) as oxidant with the aim to identify the most active
species for epoxidation and to retrieve insight into the most plausible
epoxidation mechanism. The reaction mixture is composed of various
inactive and active complexes in which vanadium may either have
oxidation state +IV or +V. Inactive species are activated with TBHP to
form active complexes. After reaction with cyclohexene, each active
species transforms back into an inactive complex that may be reactivated
again. The reaction mixture is quite complex containing hydroxyl, acetyl
acetonate, acetate, or a tert-butoxide anion as ligands, and thus,
various ligand exchange reactions may occur among active and inactive
complexes. Also, radical decomposition reactions allow transforming V+IV
to V+V species. To obtain insight into the most abundant active
complexes, each of previous transformation steps has been modeled
through thermodynamic equilibrium steps. To unravel the nature of the
most plausible epoxidation mechanism, first principle chemical kinetics
calculations have been performed on all proposed epoxidation pathways.
Our results allow to conclude that the concerted Sharpless mechanism is
the preferred reaction mechanism and that alkylperoxo species
V+IVO(L)(OOtBu) and V+VO(L-1)(L-2)(OOtBu) species are most abundant. At
the onset of the catalytic cycle, vanadium +IV species may play an
active role, but as the reaction proceeds, reaction mechanisms that
involve vanadium +V species are preferred as the acetyl acetonate is
readily oxidized. Additionally, an experimental IR and kinetic study has
been performed to give a qualitative composition of the reaction mixture
and to obtain experimental kinetic data for comparison with our
theoretical values. The agreement between theory and experiment is
satisfactory. (C) 2012 Elsevier Inc. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
catalytic system vanadyl acetylacetonate (VO(acac)(2)) with tert-butyl
hydroperoxide (TBHP) as oxidant with the aim to identify the most active
species for epoxidation and to retrieve insight into the most plausible
epoxidation mechanism. The reaction mixture is composed of various
inactive and active complexes in which vanadium may either have
oxidation state +IV or +V. Inactive species are activated with TBHP to
form active complexes. After reaction with cyclohexene, each active
species transforms back into an inactive complex that may be reactivated
again. The reaction mixture is quite complex containing hydroxyl, acetyl
acetonate, acetate, or a tert-butoxide anion as ligands, and thus,
various ligand exchange reactions may occur among active and inactive
complexes. Also, radical decomposition reactions allow transforming V+IV
to V+V species. To obtain insight into the most abundant active
complexes, each of previous transformation steps has been modeled
through thermodynamic equilibrium steps. To unravel the nature of the
most plausible epoxidation mechanism, first principle chemical kinetics
calculations have been performed on all proposed epoxidation pathways.
Our results allow to conclude that the concerted Sharpless mechanism is
the preferred reaction mechanism and that alkylperoxo species
V+IVO(L)(OOtBu) and V+VO(L-1)(L-2)(OOtBu) species are most abundant. At
the onset of the catalytic cycle, vanadium +IV species may play an
active role, but as the reaction proceeds, reaction mechanisms that
involve vanadium +V species are preferred as the acetyl acetonate is
readily oxidized. Additionally, an experimental IR and kinetic study has
been performed to give a qualitative composition of the reaction mixture
and to obtain experimental kinetic data for comparison with our
theoretical values. The agreement between theory and experiment is
satisfactory. (C) 2012 Elsevier Inc. All rights reserved.
Vanduyfhuys, L; Verstraelen, T; Vandichel, M; Waroquier, M; Speybroeck, V Van
Ab Initio Parametrized Force Field for the Flexible Metal-Organic Framework MIL-53(Al) Journal Article
In: JOURNAL OF CHEMICAL THEORY AND COMPUTATION, vol. 8, no. 9, pp. 3217-3231, 2012, ISSN: 1549-9618.
@article{ISI:000308830700026,
title = {Ab Initio Parametrized Force Field for the Flexible Metal-Organic
Framework MIL-53(Al)},
author = {L Vanduyfhuys and T Verstraelen and M Vandichel and M Waroquier and V Van Speybroeck},
doi = {10.1021/ct300172m},
issn = {1549-9618},
year = {2012},
date = {2012-09-01},
journal = {JOURNAL OF CHEMICAL THEORY AND COMPUTATION},
volume = {8},
number = {9},
pages = {3217-3231},
abstract = {A force field is proposed for the flexible metal-organic framework
MIL-53(Al), which is calibrated using density functional theory
calculations on nonperiodic clusters. The force field has three main
contributions: an electrostatic term based on atomic charges derived
with a modified Hirshfeld-I method, a van der Waals (vdW) term with
parameters taken from the MM3 model, and a valence force field whose
parameters were estimated with a new methodology that uses the gradients
and Hessian matrix elements retrieved from nonperiodic cluster
calculations. The new force field predicts geometries and cell
parameters that compare well with the experimental values both for the
large and narrow pore phases. The energy profile along the breathing
mode of the empty material reveals the existence of two minima, which
confirms the intrinsic bistable behavior of the MIL-53. Even without the
stimulus of external guest molecules, the material may transform from
the large pore (lp) to the narrow pore (np) phase [Liu et al. J. Am.
Chem. Soc. 2008, 120, 11813]. The relative stability of the two phases
critically depends on the vdW parameters, and the MM3 dispersion
interaction has the tendency to overstabilize the np phase.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
MIL-53(Al), which is calibrated using density functional theory
calculations on nonperiodic clusters. The force field has three main
contributions: an electrostatic term based on atomic charges derived
with a modified Hirshfeld-I method, a van der Waals (vdW) term with
parameters taken from the MM3 model, and a valence force field whose
parameters were estimated with a new methodology that uses the gradients
and Hessian matrix elements retrieved from nonperiodic cluster
calculations. The new force field predicts geometries and cell
parameters that compare well with the experimental values both for the
large and narrow pore phases. The energy profile along the breathing
mode of the empty material reveals the existence of two minima, which
confirms the intrinsic bistable behavior of the MIL-53. Even without the
stimulus of external guest molecules, the material may transform from
the large pore (lp) to the narrow pore (np) phase [Liu et al. J. Am.
Chem. Soc. 2008, 120, 11813]. The relative stability of the two phases
critically depends on the vdW parameters, and the MM3 dispersion
interaction has the tendency to overstabilize the np phase.
Ghysels, An; Vandichel, Matthias; Verstraelen, Toon; van der Veen, Monique A; Vos, Dirk E De; Waroquier, Michel; Speybroeck, Veronique Van
Host-guest and guest-guest interactions between xylene isomers confined in the MIL-47(V) pore system Journal Article
In: THEORETICAL CHEMISTRY ACCOUNTS, vol. 131, no. 7, 2012, ISSN: 1432-881X.
@article{ISI:000307274300002,
title = {Host-guest and guest-guest interactions between xylene isomers confined
in the MIL-47(V) pore system},
author = {An Ghysels and Matthias Vandichel and Toon Verstraelen and Monique A van der Veen and Dirk E De Vos and Michel Waroquier and Veronique Van Speybroeck},
doi = {10.1007/s00214-012-1234-7},
issn = {1432-881X},
year = {2012},
date = {2012-07-01},
journal = {THEORETICAL CHEMISTRY ACCOUNTS},
volume = {131},
number = {7},
abstract = {The porous MIL-47 material shows a selective adsorption behavior for
para-, ortho-, and meta-isomers of xylenes, making the material a
serious candidate for separation applications. The origin of the
selectivity lies in the differences in interactions (energetic) and
confining (entropic). This paper investigates the xylene-framework
interactions and the xylene-xylene interactions with quantum mechanical
calculations, using a dispersion-corrected density functional and
periodic boundary conditions to describe the crystal. First, the
strength and geometrical characteristics of the optimal xylene-xylene
interactions are quantified by studying the pure and mixed pairs in gas
phase. An extended set of initial structures is created and optimized to
sample as many relative orientations and distances as possible. Next,
the pairs are brought in the pores of MIL-47. The interaction with the
terephthalic linkers and other xylenes increases the stacking energy in
gas phase (-31.7 kJ/mol per pair) by roughly a factor four in the fully
loaded state (-58.3 kJ/mol per xylene). Our decomposition of the
adsorption energy shows various trends in the contributing xylene-xylene
interactions. The absence of a significant difference in energetics
between the isomers indicates that entropic effects must be mainly
responsible for the separation behavior.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
para-, ortho-, and meta-isomers of xylenes, making the material a
serious candidate for separation applications. The origin of the
selectivity lies in the differences in interactions (energetic) and
confining (entropic). This paper investigates the xylene-framework
interactions and the xylene-xylene interactions with quantum mechanical
calculations, using a dispersion-corrected density functional and
periodic boundary conditions to describe the crystal. First, the
strength and geometrical characteristics of the optimal xylene-xylene
interactions are quantified by studying the pure and mixed pairs in gas
phase. An extended set of initial structures is created and optimized to
sample as many relative orientations and distances as possible. Next,
the pairs are brought in the pores of MIL-47. The interaction with the
terephthalic linkers and other xylenes increases the stacking energy in
gas phase (-31.7 kJ/mol per pair) by roughly a factor four in the fully
loaded state (-58.3 kJ/mol per xylene). Our decomposition of the
adsorption energy shows various trends in the contributing xylene-xylene
interactions. The absence of a significant difference in energetics
between the isomers indicates that entropic effects must be mainly
responsible for the separation behavior.
der Mynsbrugge, Jeroen Van; Hemelsoet, Karen; Vandichel, Matthias; Waroquier, Michel; Speybroeck, Veronique Van
Efficient Approach for the Computational Study of Alcohol and Nitrile Adsorption in H-ZSM-5 Journal Article
In: JOURNAL OF PHYSICAL CHEMISTRY C, vol. 116, no. 9, pp. 5499-5508, 2012, ISSN: 1932-7447.
@article{ISI:000301315700028,
title = {Efficient Approach for the Computational Study of Alcohol and Nitrile
Adsorption in H-ZSM-5},
author = {Jeroen Van der Mynsbrugge and Karen Hemelsoet and Matthias Vandichel and Michel Waroquier and Veronique Van Speybroeck},
doi = {10.1021/jp2123828},
issn = {1932-7447},
year = {2012},
date = {2012-03-01},
journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
volume = {116},
number = {9},
pages = {5499-5508},
abstract = {Since many industrially important processes start with the adsorption of
guest molecules inside the pores of an acidic zeolite catalyst, a proper
estimate of the adsorption enthalpy is of paramount importance. In this
contribution, we report ab initio calculations on the adsorption of
water, alcohols, and nitriles at the bridging Bronsted sites of H-ZSM-5,
using both cluster and periodic models to account for the zeolite
environment. Stabilization of the adsorption complexes results from
hydrogen bonding between the guest molecule and the framework, as well
as from embedding, i.e., van der Waals interactions with the pore walls.
Large-cluster calculations with different DFT methods, in particular
B3LYP(-D), PBE(-D), M062X(-D), and omega B97X-D, are tested for their
ability to reproduce the experimental heats of adsorption available in
the literature (J. Phys. Chem. B 1997, 101, 3811-3817). A proper account
of dispersion interactions is found to be crucial to describe the
experimental trend across a series of adsorbates of increasing size,
i.e., an increase in adsorption enthalpy by 10-15 kJ/mol for each
additional carbon atom. The extended-cluster model is shown to offer an
attractive alternative to periodic simulations on the entire H-ZSM-5
unit cell, resulting in virtually identical final adsorption enthalpies.
Comparing calculated stretch frequencies of the zeolite acid sites and
the adsorbate functional groups with experimental IR data additionally
confirms that the cluster approach provides an appropriate
representation of the adsorption complexes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
guest molecules inside the pores of an acidic zeolite catalyst, a proper
estimate of the adsorption enthalpy is of paramount importance. In this
contribution, we report ab initio calculations on the adsorption of
water, alcohols, and nitriles at the bridging Bronsted sites of H-ZSM-5,
using both cluster and periodic models to account for the zeolite
environment. Stabilization of the adsorption complexes results from
hydrogen bonding between the guest molecule and the framework, as well
as from embedding, i.e., van der Waals interactions with the pore walls.
Large-cluster calculations with different DFT methods, in particular
B3LYP(-D), PBE(-D), M062X(-D), and omega B97X-D, are tested for their
ability to reproduce the experimental heats of adsorption available in
the literature (J. Phys. Chem. B 1997, 101, 3811-3817). A proper account
of dispersion interactions is found to be crucial to describe the
experimental trend across a series of adsorbates of increasing size,
i.e., an increase in adsorption enthalpy by 10-15 kJ/mol for each
additional carbon atom. The extended-cluster model is shown to offer an
attractive alternative to periodic simulations on the entire H-ZSM-5
unit cell, resulting in virtually identical final adsorption enthalpies.
Comparing calculated stretch frequencies of the zeolite acid sites and
the adsorbate functional groups with experimental IR data additionally
confirms that the cluster approach provides an appropriate
representation of the adsorption complexes.
Vermoortele, Frederik; Vandichel, Matthias; de Voorde, Ben Van; Ameloot, Rob; Waroquier, Michel; Speybroeck, Veronique Van; Vos, Dirk E De
Electronic Effects of Linker Substitution on Lewis Acid Catalysis with Metal-Organic Frameworks Journal Article
In: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, vol. 51, no. 20, pp. 4887-4890, 2012, ISSN: 1433-7851.
@article{ISI:000303925200019,
title = {Electronic Effects of Linker Substitution on Lewis Acid Catalysis with
Metal-Organic Frameworks},
author = {Frederik Vermoortele and Matthias Vandichel and Ben Van de Voorde and Rob Ameloot and Michel Waroquier and Veronique Van Speybroeck and Dirk E De Vos},
doi = {10.1002/anie.201108565},
issn = {1433-7851},
year = {2012},
date = {2012-01-01},
journal = {ANGEWANDTE CHEMIE-INTERNATIONAL EDITION},
volume = {51},
number = {20},
pages = {4887-4890},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Leus, Karen; Vandichel, Matthias; Liu, Ying-Ya; Muylaert, Ilke; Musschoot, Jan; Pyl, Steven; Vrielinck, Henk; Callens, Freddy; Marin, Guy B; Detavernier, Christophe; Wiper, Paul V; Khimyak, Yaroslav Z; Waroquier, Michel; Speybroeck, Veronique Van; der Voort, Pascal Van
The coordinatively saturated vanadium MIL-47 as a low leaching heterogeneous catalyst in the oxidation of cyclohexene Journal Article
In: JOURNAL OF CATALYSIS, vol. 285, no. 1, pp. 196-207, 2012, ISSN: 0021-9517.
@article{ISI:000300074300022,
title = {The coordinatively saturated vanadium MIL-47 as a low leaching
heterogeneous catalyst in the oxidation of cyclohexene},
author = {Karen Leus and Matthias Vandichel and Ying-Ya Liu and Ilke Muylaert and Jan Musschoot and Steven Pyl and Henk Vrielinck and Freddy Callens and Guy B Marin and Christophe Detavernier and Paul V Wiper and Yaroslav Z Khimyak and Michel Waroquier and Veronique Van Speybroeck and Pascal Van der Voort},
doi = {10.1016/j.jcat.2011.09.014},
issn = {0021-9517},
year = {2012},
date = {2012-01-01},
journal = {JOURNAL OF CATALYSIS},
volume = {285},
number = {1},
pages = {196-207},
abstract = {A Metal Organic Framework, containing coordinatively saturated sites
linked together by terephthalic linkers (V-MIL-47), is evaluated as a
catalyst in the epoxidation of cyclohexene. Different solvents and
conditions are tested and compared. If the oxidant TBHP is dissolved in
water, a significant leaching of V-species into the solution is
observed, and also radical pathways are prominently operative leading to
the formation of an adduct between the peroxide and cyclohexene. If,
however, the oxidant is dissolved in decane, leaching is negligible and
the structural integrity of the V-MIL-47 is maintained during successive
runs. The selectivity toward the epoxide is very high in these
circumstances. Extensive computational modeling is performed to show
that several reaction cycles are possible. EPR and NMR measurements
confirm that at least two parallel catalytic cycles are co-existing: one
with V+IV sites and one with pre-oxidized V+V sites, and this is in
complete agreement with the theoretical predictions. (C) 2011 Elsevier
Inc. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
linked together by terephthalic linkers (V-MIL-47), is evaluated as a
catalyst in the epoxidation of cyclohexene. Different solvents and
conditions are tested and compared. If the oxidant TBHP is dissolved in
water, a significant leaching of V-species into the solution is
observed, and also radical pathways are prominently operative leading to
the formation of an adduct between the peroxide and cyclohexene. If,
however, the oxidant is dissolved in decane, leaching is negligible and
the structural integrity of the V-MIL-47 is maintained during successive
runs. The selectivity toward the epoxide is very high in these
circumstances. Extensive computational modeling is performed to show
that several reaction cycles are possible. EPR and NMR measurements
confirm that at least two parallel catalytic cycles are co-existing: one
with V+IV sites and one with pre-oxidized V+V sites, and this is in
complete agreement with the theoretical predictions. (C) 2011 Elsevier
Inc. All rights reserved.
Leus, Karen; Couck, Sarah; Vandichel, Matthias; Vanhaelewyn, Gauthier; Liu, Ying-Ya; Marin, Guy B; Driessche, Isabel Van; Depla, Diederik; Waroquier, Michel; Speybroeck, Veronique Van; Denayer, Joeri F M; Voort, Pascal Van Der
Synthesis, characterization and sorption properties of NH2-MIL-47 Journal Article
In: PHYSICAL CHEMISTRY CHEMICAL PHYSICS, vol. 14, no. 44, pp. 15562-15570, 2012, ISSN: 1463-9076.
@article{ISI:000310153300037,
title = {Synthesis, characterization and sorption properties of NH2-MIL-47},
author = {Karen Leus and Sarah Couck and Matthias Vandichel and Gauthier Vanhaelewyn and Ying-Ya Liu and Guy B Marin and Isabel Van Driessche and Diederik Depla and Michel Waroquier and Veronique Van Speybroeck and Joeri F M Denayer and Pascal Van Der Voort},
doi = {10.1039/c2cp42137b},
issn = {1463-9076},
year = {2012},
date = {2012-01-01},
journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS},
volume = {14},
number = {44},
pages = {15562-15570},
abstract = {An amino functionalized vanadium-containing Metal Organic Framework,
NH2-MIL-47, has been synthesized by a hydrothermal reaction in an
autoclave. Alternatively, a synthesis route via microwave enhanced
irradiation has been optimized to accelerate the synthesis. The
NH2-MIL-47 exhibits the same topology as MIL-47, in which the V center
is octahedrally coordinated. After an exchange procedure in DMF the
V+III center is oxidized to V+IV, which is confirmed by EPR and XPS
measurements. The CO2 and CH4 adsorption properties have been evaluated
and compared to MIL-47, showing that both MOFs have an almost similar
adsorption capacity and affinity for CO2. DFT-based molecular modeling
calculations were performed to obtain more insight into the adsorption
positions for CO2 in NH2-MIL-47. Furthermore our calculated adsorption
enthalpies agree well with the experimental values.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
NH2-MIL-47, has been synthesized by a hydrothermal reaction in an
autoclave. Alternatively, a synthesis route via microwave enhanced
irradiation has been optimized to accelerate the synthesis. The
NH2-MIL-47 exhibits the same topology as MIL-47, in which the V center
is octahedrally coordinated. After an exchange procedure in DMF the
V+III center is oxidized to V+IV, which is confirmed by EPR and XPS
measurements. The CO2 and CH4 adsorption properties have been evaluated
and compared to MIL-47, showing that both MOFs have an almost similar
adsorption capacity and affinity for CO2. DFT-based molecular modeling
calculations were performed to obtain more insight into the adsorption
positions for CO2 in NH2-MIL-47. Furthermore our calculated adsorption
enthalpies agree well with the experimental values.
2011
Speybroeck, Veronique Van; der Mynsbrugge, Jeroen Van; Vandichel, Matthias; Hemelsoet, Karen; Lesthaeghe, David; Ghysels, An; Marin, Guy B; Waroquier, Michel
First Principle Kinetic Studies of Zeolite-Catalyzed Methylation Reactions Journal Article
In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 133, no. 4, pp. 888-899, 2011, ISSN: 0002-7863.
@article{ISI:000287295300051,
title = {First Principle Kinetic Studies of Zeolite-Catalyzed Methylation
Reactions},
author = {Veronique Van Speybroeck and Jeroen Van der Mynsbrugge and Matthias Vandichel and Karen Hemelsoet and David Lesthaeghe and An Ghysels and Guy B Marin and Michel Waroquier},
doi = {10.1021/ja1073992},
issn = {0002-7863},
year = {2011},
date = {2011-02-01},
journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
volume = {133},
number = {4},
pages = {888-899},
abstract = {Methylations of ethene, propene, and butene by methanol over the acidic
microporous H-ZSM-5 catalyst are studied by means of state of the art
computational techniques, to derive Arrhenius plots and rate constants
from first principles that can directly be compared with the
experimental data. For these key elementary reactions in the methanol to
hydrocarbons (MTH) process, direct kinetic data became available only
recently [J. Catal. 2005, 224, 115-123; J. Catal. 2005, 234, 385-400].
At 350 degrees C, apparent activation energies of 103, 69, and 45 kJ/mol
and rate constants of 2.6 x 10(-4), 4.5 x 10(-3), and 1.3 x 10(-2)
mol/(g h mbar) for ethene, propene, and butene were ;derived, giving
following relative ratios for methylation k(ethene)/k(propene)/k(butene) = 1:17:50. In this work, rate constants including pre-exponential
factors are calculated which give very good agreement with the
experimental data: apparent activation energies of 94, 62, and 37 kJ/mol
for ethene, propene, and butene are found, and relative ratios of methylation k(ethene)/k(propene)/k(butene) = 1:23:763. The entropies of
gas phase alkenes are underestimated in the harmonic oscillator
approximation due to the occurrence of internal rotations. These low
vibrational modes were substituted by manually constructed partition
functions. Overall, the absolute reaction rates can be calculated with
near chemical accuracy, and qualitative trends are very well reproduced.
In addition, the proposed scheme is computationally very efficient and
constitutes significant progress in kinetic modeling of reactions in
heterogeneous catalysis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
microporous H-ZSM-5 catalyst are studied by means of state of the art
computational techniques, to derive Arrhenius plots and rate constants
from first principles that can directly be compared with the
experimental data. For these key elementary reactions in the methanol to
hydrocarbons (MTH) process, direct kinetic data became available only
recently [J. Catal. 2005, 224, 115-123; J. Catal. 2005, 234, 385-400].
At 350 degrees C, apparent activation energies of 103, 69, and 45 kJ/mol
and rate constants of 2.6 x 10(-4), 4.5 x 10(-3), and 1.3 x 10(-2)
mol/(g h mbar) for ethene, propene, and butene were ;derived, giving
following relative ratios for methylation k(ethene)/k(propene)/k(butene) = 1:17:50. In this work, rate constants including pre-exponential
factors are calculated which give very good agreement with the
experimental data: apparent activation energies of 94, 62, and 37 kJ/mol
for ethene, propene, and butene are found, and relative ratios of methylation k(ethene)/k(propene)/k(butene) = 1:23:763. The entropies of
gas phase alkenes are underestimated in the harmonic oscillator
approximation due to the occurrence of internal rotations. These low
vibrational modes were substituted by manually constructed partition
functions. Overall, the absolute reaction rates can be calculated with
near chemical accuracy, and qualitative trends are very well reproduced.
In addition, the proposed scheme is computationally very efficient and
constitutes significant progress in kinetic modeling of reactions in
heterogeneous catalysis.
Lesthaeghe, David; der Mynsbrugge, Jeroen Van; Vandichel, Matthias; Waroquier, Michel; Speybroeck, Veronique Van
Full Theoretical Cycle for both Ethene and Propene Formation during Methanol-to-Olefin Conversion in H-ZSM-5 Journal Article
In: CHEMCATCHEM, vol. 3, no. 1, pp. 208-212, 2011, ISSN: 1867-3880.
@article{ISI:000285888500026,
title = {Full Theoretical Cycle for both Ethene and Propene Formation during
Methanol-to-Olefin Conversion in H-ZSM-5},
author = {David Lesthaeghe and Jeroen Van der Mynsbrugge and Matthias Vandichel and Michel Waroquier and Veronique Van Speybroeck},
doi = {10.1002/cctc.201000286},
issn = {1867-3880},
year = {2011},
date = {2011-01-01},
journal = {CHEMCATCHEM},
volume = {3},
number = {1},
pages = {208-212},
abstract = {The methanol-to-olefin (MTO) process, catalyzed by acidic zeolites such
as H-ZSM-5, provides an increasingly important alternative to the
production of light olefins from crude oil. However, the various
mechanistic proposals for methanol-to-olefin conversion have been
strongly disputed for the past several decades. This work provides
theoretical evidence that the experimentally suggested `alkene cycle',
part of a co-catalytic hydrocarbon pool, offers a viable path to the
production of both propene and ethene, in stark contrast to the
often-proposed direct mechanisms. This specific proposal hinges on
repeated methylation reactions of alkenes, starting from propene, which
occur easily within the zeolite environment. Subsequent cracking steps
regenerate the original propene molecule, while also forming new propene
and ethene molecules as primary products. Because the host framework
stabilizes intermediate carbenium ions, isomerization and de-protonation
reactions are extremely fast. Combined with earlier joint experimental
and theoretical work on polymethylbenzenes as active hydrocarbon pool
species, it is clear that, in zeolite H-ZSM-5, multiple parallel and
interlinked routes operate on a competitive basis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
as H-ZSM-5, provides an increasingly important alternative to the
production of light olefins from crude oil. However, the various
mechanistic proposals for methanol-to-olefin conversion have been
strongly disputed for the past several decades. This work provides
theoretical evidence that the experimentally suggested `alkene cycle',
part of a co-catalytic hydrocarbon pool, offers a viable path to the
production of both propene and ethene, in stark contrast to the
often-proposed direct mechanisms. This specific proposal hinges on
repeated methylation reactions of alkenes, starting from propene, which
occur easily within the zeolite environment. Subsequent cracking steps
regenerate the original propene molecule, while also forming new propene
and ethene molecules as primary products. Because the host framework
stabilizes intermediate carbenium ions, isomerization and de-protonation
reactions are extremely fast. Combined with earlier joint experimental
and theoretical work on polymethylbenzenes as active hydrocarbon pool
species, it is clear that, in zeolite H-ZSM-5, multiple parallel and
interlinked routes operate on a competitive basis.
2010
Vandichel, Matthias; Lesthaeghe, David; der Mynsbrugge, Jeroen Van; Waroquier, Michel; Speybroeck, Veronique Van
Assembly of cyclic hydrocarbons from ethene and propene in acid zeolite catalysis to produce active catalytic sites for MTO conversion Journal Article
In: JOURNAL OF CATALYSIS, vol. 271, no. 1, pp. 67-78, 2010, ISSN: 0021-9517.
@article{ISI:000277217500008,
title = {Assembly of cyclic hydrocarbons from ethene and propene in acid zeolite
catalysis to produce active catalytic sites for MTO conversion},
author = {Matthias Vandichel and David Lesthaeghe and Jeroen Van der Mynsbrugge and Michel Waroquier and Veronique Van Speybroeck},
doi = {10.1016/j.jcat.2010.02.001},
issn = {0021-9517},
year = {2010},
date = {2010-04-01},
journal = {JOURNAL OF CATALYSIS},
volume = {271},
number = {1},
pages = {67-78},
abstract = {The formation of cyclic hydrocarbons from smaller building blocks such
as ethene and propene is investigated in protonated ZSM-5, using a
2-layered ONIOM(B3LYP/6-31+g(d):HF/6-31+g(d)) approach and an additional
Grimme-type van der Waals dispersion correction term to account for the
long-range dispersion interactions. These cyclic species form precursors
for active hydrocarbon pool species and play a key role in activating
the acidic zeolite host for successful methanol-to-olefin (MTO)
conversion. Starting from trace amounts of ethene and propene that are
formed during an initial induction period or during the active phase,
dimerization reactions allow for rapid chain growth. The products of
these reactions can be neutral alkenes, framework-bound alkoxide species
or intermediate carbenium ions, depending on the zeolite environment
taken into account. On the basis of rate constants for successive
reaction steps, a viable route toward cyclization is proposed, which
starts from the formation of a framework-bound propoxide from propene,
followed by dimerization with an additional propene molecule to form the
2-hexyl carbenium ion which finally undergoes ring closure to yield
methylcyclopentane. This cyclic species in turn forms a precursor for
either an active hydrocarbon pool compound or for deactivating coke
deposit. (C) 2010 Elsevier Inc. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
as ethene and propene is investigated in protonated ZSM-5, using a
2-layered ONIOM(B3LYP/6-31+g(d):HF/6-31+g(d)) approach and an additional
Grimme-type van der Waals dispersion correction term to account for the
long-range dispersion interactions. These cyclic species form precursors
for active hydrocarbon pool species and play a key role in activating
the acidic zeolite host for successful methanol-to-olefin (MTO)
conversion. Starting from trace amounts of ethene and propene that are
formed during an initial induction period or during the active phase,
dimerization reactions allow for rapid chain growth. The products of
these reactions can be neutral alkenes, framework-bound alkoxide species
or intermediate carbenium ions, depending on the zeolite environment
taken into account. On the basis of rate constants for successive
reaction steps, a viable route toward cyclization is proposed, which
starts from the formation of a framework-bound propoxide from propene,
followed by dimerization with an additional propene molecule to form the
2-hexyl carbenium ion which finally undergoes ring closure to yield
methylcyclopentane. This cyclic species in turn forms a precursor for
either an active hydrocarbon pool compound or for deactivating coke
deposit. (C) 2010 Elsevier Inc. All rights reserved.
Leus, Karen; Muylaert, Ilke; Vandichel, Matthias; Marin, Guy B; Waroquier, Michel; Speybroeck, Veronique Van; der Voort, Pascal Van
The remarkable catalytic activity of the saturated metal organic framework V-MIL-47 in the cyclohexene oxidation Journal Article
In: CHEMICAL COMMUNICATIONS, vol. 46, no. 28, pp. 5085-5087, 2010, ISSN: 1359-7345.
@article{ISI:000279565500010,
title = {The remarkable catalytic activity of the saturated metal organic
framework V-MIL-47 in the cyclohexene oxidation},
author = {Karen Leus and Ilke Muylaert and Matthias Vandichel and Guy B Marin and Michel Waroquier and Veronique Van Speybroeck and Pascal Van der Voort},
doi = {10.1039/c0cc01506g},
issn = {1359-7345},
year = {2010},
date = {2010-01-01},
journal = {CHEMICAL COMMUNICATIONS},
volume = {46},
number = {28},
pages = {5085-5087},
abstract = {The remarkable catalytic activity of the saturated metal organic
framework MIL-47 in the epoxidation of cyclohexene is elucidated by
means of both experimental results and theoretical calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
framework MIL-47 in the epoxidation of cyclohexene is elucidated by
means of both experimental results and theoretical calculations.
2009
Hemelsoet, Karen; Nollet, Arno; Vandichel, Matthias; Lesthaeghe, David; Speybroeck, Veronique Van; Waroquier, Michel
The Effect of Confined Space on the Growth of Naphthalenic Species in a Chabazite-Type Catalyst: A Molecular Modeling Study Journal Article
In: CHEMCATCHEM, vol. 1, no. 3, pp. 373-378, 2009, ISSN: 1867-3880.
@article{ISI:000274154100006,
title = {The Effect of Confined Space on the Growth of Naphthalenic Species in a
Chabazite-Type Catalyst: A Molecular Modeling Study},
author = {Karen Hemelsoet and Arno Nollet and Matthias Vandichel and David Lesthaeghe and Veronique Van Speybroeck and Michel Waroquier},
doi = {10.1002/cctc.200900208},
issn = {1867-3880},
year = {2009},
date = {2009-11-01},
journal = {CHEMCATCHEM},
volume = {1},
number = {3},
pages = {373-378},
abstract = {Methylation reactions of naphthalenic species over the acidic
microporous zeolite with chabazite topology have been investigated by
means of two-layered ab initio computations. Large cluster results
combined with van der Waals contributions provide thermodynamic and
kinetic results of successive methylation steps. The growth of fused
bicyclic species is important as these can act as hydrocarbon pool
species within the methanol-to-olefin (MTO) process, but ultimately
leads to the deactivation of the catalyst. The influence of the confined
space of the zeolite pore on the resulting transition state or product
shape selectivity is investigated in detail.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
microporous zeolite with chabazite topology have been investigated by
means of two-layered ab initio computations. Large cluster results
combined with van der Waals contributions provide thermodynamic and
kinetic results of successive methylation steps. The growth of fused
bicyclic species is important as these can act as hydrocarbon pool
species within the methanol-to-olefin (MTO) process, but ultimately
leads to the deactivation of the catalyst. The influence of the confined
space of the zeolite pore on the resulting transition state or product
shape selectivity is investigated in detail.