Center for Molecular Modeling - P. Valvekens

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

Base catalytic activity of alkaline earth MOFs: a (micro)spectroscopic study of active site formation by the controlled transformation of structural anions

michel — Tue, 20 May 2014 12:44:05 +0000

P. Valvekens, D. Jonckheere, T. De Baerdemaeker, A. Kubarev, M. Vandichel, K. Hemelsoet, M. Waroquier, V. Van Speybroeck, E. Smolders, D. Depla, D. Roeffaers, D. De Vos

Chemical Science

5 (11), 4517-4524

2014

Abstract

A new concept has been developed for generating highly dispersed base sites on metal-organic framework (MOF) lattices. The base catalytic activity of two alkaline earth MOFs, M2(BTC)(NO3)(DMF) (M = Ba or Sr, H3BTC = 1,3,5-benzenetricarboxylic acid, DMF = N,N-dimethylformamide) was studied as a function of their activation procedure. The catalytic activity in Knoevenagel condensation and Michael addition reactions was found to increase strongly with activation temperature. Physicochemical characterization using FTIR, 13C CP MAS NMR, PXRD, XPS, TGA-MS, SEM, EPR, N2 physisorption and nitrate content analysis shows that during activation, up to 85 % of the nitrate anions are selectively removed from the structure and replaced with other charge compensating anions such as O2-. The defect sites generated via this activation act as new strong basic sites within the catalyst structure. A fluorescence microscopic visualization of the activity convincingly proves that the activity is exclusively associated with the hexagonal crystals, and that reaction proceeds inside the crystal’s interior. Theoretical analysis of the Ba-material shows that the basicity of the proposed Ba2+-O2--Ba2+ motives is close to that of edge sites in BaO.

DOI

http://dx.doi.org/10.1039/C4SC01731E

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14_ChemScience_5(11)4524_Valvekens.pdf

Metal-dioxidoterephthalate MOFs of the MOF-74 type: microporous basic catalysts with well-defined active sites

michel — Mon, 10 Feb 2014 15:01:30 +0000

P. Valvekens, M. Vandichel, M. Waroquier, V. Van Speybroeck, D. De Vos

Journal of Catalysis

317, 1–10

2014

Abstract

The hybrid frameworks M2dobdc (dobdc4− = 2,5-dioxidoterephthalate, M2+ = Mg2+, Co2+, Ni2+, Cu2+ and Zn2+), commonly known as CPO-27 or MOF-74, are shown to be active catalysts in base-catalyzed reactions such as Knoevenagel condensations or Michael additions. Rather than utilizing N-functionalized linkers as a source of basicity, the intrinsic basicity of these materials arises from the presence of the phenolate oxygen atoms coordinated to the metal ions. The overall activity is due to a complex interplay of the basic properties of these structural phenolates and the reactant binding characteristics of the coordinatively unsaturated sites. The nature of the active site and the order of activity between the different M2dobdc materials were rationalized via computational efforts; the most active material, both in theory and in experiment, is the Ni-containing variant. The basicity of Ni2dobdc was experimentally proven by chemisorption of pyrrole and observation by IR spectroscopy.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1016/j.jcat.2014.06.006

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final_published_1-s2.0-S0021951714001614-main.pdf

Enhanced base catalytic activity of M2(BTC)(NO3)(DMF) via controlled structure modification

mat — Wed, 05 Nov 2014 10:11:33 +0000

D. Jonckheere, P. Valvekens, T. De Baerdemaeker, A. Kubarev, M. Vandichel, K. Hemelsoet, M. Waroquier, V. Van Speybroeck, M. Roeffaers, D. De Vos

P19

ISBN/ISSN:

Poster

Conference / event / venue

DZA2014

Ghent, Belgium

Tuesday, 7 October, 2014

Imparting base catalytic activity in alkaline earth MOFs by selectively transforming structural anions into active sites

hemel — Thu, 09 Oct 2014 14:01:12 +0000

P. Valvekens, K. Hemelsoet

ISBN/ISSN:

Talk

Conference / event / venue

IAP P 07/05 annual scientific meeting

Louvain La Neuve, Belgium

Friday, 19 September, 2014

Modulating active sites in MOFs for improved Lewis acid or base catalysis

wim — Thu, 10 Apr 2014 09:44:08 +0000

F. Vermoortele, P. Valvekens, A. Vimont, V. Van Speybroeck

1116-INOR

ISBN/ISSN: 0065-7727

Talk

Conference / event / venue

245th National Spring Meeting of the American-Chemical-Society (ACS)

New Orleans, USA

Sunday, 7 April, 2013 to Thursday, 11 April, 2013

Conference reference

ACS Spring 2013

A new approach towards basic metal-organic frameworks

mat — Mon, 28 Jan 2013 09:07:16 +0000

P. Valvekens, M. Vandichel, M. Waroquier, V. Van Speybroeck, D. De Vos

ISBN/ISSN:

Poster

Conference / event / venue

MOF2012

Edinburgh, UK

Sunday, 16 September, 2012 to Wednesday, 19 September, 2012

Abstract (private)

4011.pdf

Conference reference

MOF2012