Center for Molecular Modeling - T. Bogaerts

Systematic study of the chemical and hydrothermal stability of selected "stable" Metal Organic Frameworks

kevin — Thu, 24 Sep 2015 15:25:30 +0000

K. Leus, T. Bogaerts, J. De Decker, H. Depauw, K. Hendrickx, H. Vrielinck, V. Van Speybroeck, P. Van der Voort

Microporous and Mesoporous Materials

226, 110-116

2016

Abstract

In this work, the hydrothermal and chemical stability towards acids, bases, air, water and peroxides of Metal Organic Frameworks, that are commonly considered to be stable, is presented. As a proof of stability both the crystallinity and porosity are measured before and after exposure to the stress test. The major part of the MOFs examined in this study showed a good hydrothermal stability except for the UiO-67, NH2-MIL-101 (Al) and CuBTC material. The chemical stability towards acids and bases show a similar tendency and an ordering can be proposed as: MIL-101(Cr)>NH2-UiO-66>UiO-66>UiO-67>NH2-MIL-53>MIL-53(Al)>ZIF-8>CuBTC>NH2-MIL-101(Al). In the tests with the H2O2 solution most materials behaved poorly, only the UiO-66 and NH2-UiO-66 framework showed a good stability.

DOI

http://dx.doi.org/10.1016/j.micromeso.2015.11.055

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2016 - Leus - MMM - 226 - 110-116.pdf

Fine-tuning the theoretically predicted structure of MIL-47(V) with the aid of powder X-ray diffraction

michel — Wed, 15 Jul 2015 08:58:36 +0000

T. Bogaerts, L. Vanduyfhuys, D.E.P. Vanpoucke, J. Wieme, M. Waroquier, P. Van der Voort, V. Van Speybroeck

CrystEngComm

17, 8612–8622

2015

Abstract

The structural characterization of complex crystalline materials such as metal organic frameworks can prove a very difficult challenge both for experimentalists as for theoreticians. From theory, the flat potential energy surface of these highly flexible structures often leads to different geometries that are energetically very close to each other. In this work a distinction between various computationally determined structures is made by comparing experimental and theoretically derived X-ray diffractograms which are produced from the materials geometry. The presented approach allows to choose the most appropriate geometry of a MIL-47(V) MOF and even distinguish between different electronic configurations that induce small structural changes. Moreover the techniques presented here are used to verify the applicability of a newly developed force field for this material. The discussed methodology is of significant importance for modelling studies where accurate geometries are crucial, such as mechanical properties and adsorption of guest molecules.

DOI

http://dx.doi.org/10.1039/C5CE01388G

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authorreprints.pdf

The enantioselectivity of the manganese-salen complex in the epoxidation of unfunctionalized olefins and the influence of grafting

wim — Tue, 02 Jun 2015 07:02:43 +0000

T. Bogaerts, S. Wouters, P. Van der Voort, V. Van Speybroeck

Journal of Molecular Catalysis A: Chemical

Vol. 406, 106-113

2015

Abstract

Jacobsen’s complexes are famous for their usability for enantioselective epoxidations. However, the applicability of this catalytic system has been severely limited by several practical problems such as deactivation and separation after reaction. Grafting of Jacobsen-type complexes on solid supports is an attractive way to overcome these problems but led to a decrease in selectivity. A combined theoretical and experimental approach is presented to unravel the factors governing enantioselectivity. The importance of different substituents was determined by analyzing the transition state for the oxygen transfer using the full system as a model. An analysis of the asymmetric complex has shown an inherent tendency for a decreased selectivity due to the lack of specific bulky groups. Experimentally an immobilized Jacobsen catalyst on a metal organic framework (MIL-101) was synthesized which confirms the computational tendencies but the decrease in selectivity is limited, indicating that the MIL-101(Cr) is a suitable carrier for this complex.

Open Access version available at UGent repository

DOI

10.1016/j.molcata.2015.05.020

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15_j_mol_cat_a_chem_xxxxx_Bogaerts_manuscript.pdf

15_j_mol_cat_a_chem_xxxxx_Bogaerts.pdf

Mechanistic investigation on the oxygen transfer with the manganese-salen complex

bogaerts — Wed, 27 May 2015 11:26:57 +0000

T. Bogaerts, S. Wouters, P. Van der Voort, V. Van Speybroeck

ChemCatChem

7 (17), 2711–2719

2015

Abstract

The most well-known application of salen complexes is the use of a chiral ligand loaded with manganese to form the Jacobsen complex. This organometallic catalyst is used in the epoxidation of unfunctionalized olefins and can achieve very high selectivities. Although this application was proposed many years ago, the mechanism of oxygen transfer remains a question until now. In this paper, the epoxidation mechanism is investigated by an ab initio kinetic modeling study. First of all a proper DFT functional is selected which yields the correct ordering of the various spin states. Our results show that the epoxidation proceeds via a radical intermediate. Starting from the radical intermediate, these results can explain the experiments with radical probes. The subtle influences in the transition state using the full Jacobsen catalyst explain the experimentally observed product distribution.

DOI

http://dx.doi.org/10.1002/cctc.201500584

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main_manuscript.pdf

Communication: DMRG-SCF study of the singlet, triplet, and quintet states of oxo-Mn(Salen)

michel — Wed, 18 Jun 2014 19:01:01 +0000

S. Wouters, T. Bogaerts, P. Van der Voort, V. Van Speybroeck, D. Van Neck

Journal of Chemical Physics

140, 241103

2014

Abstract

We use CheMPS2, our free open-source spin-adapted implementation of the density matrix renormalization group (DMRG) [S. Wouters, W. Poelmans, P. W. Ayers, and D. Van Neck, Comput. Phys. Commun. 185, 1501 (2014)], to study the lowest singlet, triplet, and quintet states of the oxo-Mn(Salen) complex. We describe how an initial approximate DMRG calculation in a large active space around the Fermi level can be used to obtain a good set of starting orbitals for subsequent complete-active-space or DMRG self-consistent field calculations. This procedure mitigates the need for a localization procedure, followed by a manual selection of the active space. Per multiplicity, the same active space of 28 electrons in 22 orbitals (28e, 22o) is obtained with the 6-31G∗ , cc-pVDZ, and ANO-RCC-VDZP basis sets (the latter with DKH2 scalar relativistic corrections). Our calculations provide new insight into the electronic structure of the quintet.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1063/1.4885815

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1405.5642v3.pdf

paper8.pdf

Mn-salen@MIL101(Al) a heterogeneous, enantioselective catalyst using a ‘bottle around the ship’ approach

bogaerts — Tue, 09 Jul 2013 09:43:07 +0000

T. Bogaerts, A. Van Yperen-De Deyne, Y-Y Liu, F. Lynen, V. Van Speybroeck, P. Van der Voort

Chemical Communications

2013 (49), 8021-8023

2013

Abstract

An enantioselective catalyst, consisting of a chiral Mn(III)salen complex entrapped in the MIL-101 metal organic framework is reported. For the first time, we assemble a robust MOF-cage around a delicate chiral complex, without affecting the structure and stability of this complex. The newly prepared heterogeneous catalyst shows the same enantioselective excess compared to the homogeneous Mn(III)salen complex and is fully recyclable. Theoretical calculations yield insight into the dimensions of the various transition states of the epoxidation reaction.

DOI

http://dx.doi.org/10.1039/C3CC44473B

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main_manuscript_pdf.pdf

13_ChemComm_49_8021_Bogaerts.pdf

Bimetallic–Organic Framework as a Zero-Leaching Catalyst in the Aerobic Oxidation of Cyclohexene

bogaerts — Tue, 09 Jul 2013 09:09:00 +0000

Y-Y Liu, K. Leus, T. Bogaerts, K. Hemelsoet, E. Bruneel, V. Van Speybroeck, P. Van der Voort

ChemCatChem

5 (12), 3657–3664

2013

Abstract

A gallium 2,2′-bipyridine-5,5′-dicarboxylate metal–organic framework (MOF), denoted as COMOC-4, has been synthesized by solvothermal synthesis. This MOF exhibits the same topology as MOF-253. CuCl₂ was incorporated into COMOC-4 by a post-synthetic modification (PSM). The spectroscopic absorption properties of the MOF framework before and after PSM were compared with theoretical data obtained by employing molecular dynamics combined with time-dependent DFT calculations on both the as-synthesized and functionalized linker. The catalytic behavior of the resulting Cu²⁺@COMOC-4 material was evaluated in the aerobic oxidation of cyclohexene with isobutyraldehyde as a co-oxidant. In addition, the catalytic performance of Cu²⁺@COMOC-4 was compared with that of the commercially available Cu-BTC (BTC=benzene-1,3,5-tricarboxylate) MOF. Cu²⁺@COMOC-4 exhibits a good cyclohexene conversion and an excellent selectivity towards cyclohexene oxide in comparison to the Cu-based reference catalyst. Furthermore, no leaching of the active Cu sites was observed during at least four consecutive runs.

DOI

http://dx.doi.org/10.1002/cctc.201300529

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manuscript.pdf

Covalent immobilization of the Jacobsen catalyst on mesoporous phenolic polymer: a highly enantioselective and stable asymmetric epoxidation catalyst

bogaerts — Tue, 12 Feb 2013 10:08:02 +0000

J. De Decker, T. Bogaerts, I. Muylaert, S. Delahaye, F. Lynen, V. Van Speybroeck, A. Verberckmoes, P. Van der Voort

Materials Chemistry and Physics

141 (2013), 967-972

2013

Abstract

The Jacobsen catalyst, N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese (III) chloride is covalently immobilized on mesoporous phenolic resin through a direct and simple procedure. The immobilization is evident from nitrogen sorption and quantitative XRF measurements. A complex loading of 0.09 mmol g−1 is obtained, corresponding to well dispersed Mn-complexes on the surface of the mesoporous phenolic resin. This novel catalytic system shows good catalytic activity and excellent enantioselectivity in the asymmetric epoxidation of 1,2-dialin. The heterogenized Jacobsen catalyst is demonstrated to be a re-usable and non-leaching catalytic system.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1016/j.matchemphys.2013.06.035

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13_matchemphys_141_967_DeDecker.pdf

draft_matchemphys.pdf

Bipyridine-Based Nanosized Metal–Organic Framework with Tunable Luminescence by a Postmodification with Eu(III): An Experimental and Theoretical Study

michel — Wed, 06 Feb 2013 12:44:57 +0000

Y-Y Liu, R. Decadt, T. Bogaerts, K. Hemelsoet, A.M. Kaczmarek, D. Poelman, M. Waroquier, V. Van Speybroeck, R. Van Deun, P. Van der Voort

Journal of Physical Chemistry C

117 (21), 11302–11310

2013

Abstract

A gallium 2,2′-bipyridine-5,5′-dicarboxylate metal-organic framework, Ga(OH)(bpydc), denoted as COMOC-4 (COMOC = Center for Ordered Materials, Organometallics and Catalysis, Ghent University) has been synthesized via solvothermal synthesis procedure. The structure has the topology of an aluminum 2,2′-bipyridine-5,5′-dicarboxylate, the so-called MOF-253. TEM and SEM micrographs show the COMOC-4 crystals are formed in nanoplates with uniform size of 30-50 nm. The UV-Vis spectra of COMOC-4 in methanol solution show maximal electronic absorption at 307 nm. This results from linker to linker transitions as elucidated by time-dependent density functional theory simulations on the linker and COMOC-4 cluster models. When excited at 400 nm, COMOC-4 displays an emission band centered at 542 nm. Upon immersion in different solvents, the emission band for the framework is shifted in the range of 525~548 nm, depending on the solvent. After incorporating Eu3+ cations, the emission band of the framework is shifted to even shorter wavelengths (505 nm). By varying the excitation wavelengths from 250 to 400 nm, we can fine-tune the emission from red to yellowish green in the CIE diagram. The luminescence behavior of Eu3+ cations is well preserved and the solid state luminescence lifetimes of λ1 = 45 µs (35.4 %) and λ2 = 162 µs (64.6 %) are observed.

DOI

http://dx.doi.org/10.1021/jp402154q

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13_jphyschemC_117_11302_Liu.pdf

Quantification of silanol sites for the most common mesoporous ordered silicas and organosilicas: total versus accessible silanols

wim — Wed, 07 Nov 2012 13:38:27 +0000

M. Ide, M. El-Roz, E. De Canck, A. Vicente, T. Planckaert, T. Bogaerts, I. Van Driessche, F. Lynen, V. Van Speybroeck, F. Thibault-Starzyk, P. Van der Voort

Physical Chemistry Chemical Physics (PCCP)

15, 642-650

2013

Abstract

IR and NMR spectroscopy were used to determine the silanol content in the most common mesoporous ordered silicas: MCM-41, MCM-48, SBA-15 and SBA-16. In addition, a spray dried MCM-41 and an ethene bridged PMO are investigated. The results are compared with a commercial chromatographic silica (Nucleosil). The complete distribution of surface and bulk silanols, and of isolated, geminal and vicinal silanols for all these materials is presented. A distinction is made between the total silanol number and the reachable or surface silanol content. The latter is determined by controlled reactions with simple silanes. All mesoporous ordered silicas, and especially the thick walled SBA-type materials and the PMO contain a surprisingly high amount of total silanol sites, albeit that up to 90% if these silanols are buried inside the walls and are not reachable for small silanes.

DOI

http://dx.doi.org/10.1039/C2CP42811C

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13_PCCP_15_642_ide.pdf