T. De Baerdemaeker

A Flexible Photoactive Titanium Metal-Organic Framework Based on a [Ti-3(IV)(mu(3)-O)(O)(2)(COO)(6)] Cluster

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
A1

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

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

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
A1

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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