Trees De Baerdemaeker

A Flexible Photoactive Titanium Metal–Organic Framework Based on a [TiIV3(μ3-O)(O)2(COO)6] Cluster

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-cyclohexanedicarboxylate linkers and an unprecedented [Ti(IV)3(μ3-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.

A new catalyst platform: zeolite Beta from template-free synthesis

Structural analysis and catalytic testing revealed that zeolite Beta from template-free synthesis introduces new possibilities in catalysis, as a result of its unprecedentedly high density of active sites with exceptional stability and distinctively ordered nature. Highly active and selective catalysts were obtained either by using it in the Al-rich form (e.g. alkylation) or after post-synthesis treatments (e.g. acylation). Such versatility made possible by this novel synthesis route constitutes a new toolbox for catalysis.

New zeolite Al-COE-4: reaching highly shape-selective catalytic performance through interlayer expansion

A ferrierite-type layered aluminosilicate, Al-RUB-36, was prepared for the first time and its interlayer expansion resulted in new zeolite catalysts denoted Al-COE-3 and Al-COE-4. Decane hydroconversion tests demonstrated the highly active and shape-selective nature of the new Al-COE-4 catalyst with an unprecedented isomerization yield, highlighting the potential of this material as a hydroisomerization catalyst. This is the first report on achieving shape-selectivity via interlayer expansion.

A new class of solid Lewis acid catalysts based on interlayer expansion of layered silicates of the RUB-36 type with heteroatoms

Interlayer expanded zeolites are derived from layered zeolite precursors by inserting a tetrahedrally coordinated atom (T-atom) in between the precursor layers. To achieve this expansion, a Si source like dichlorodimethylsilane or diethoxydimethylsilane is typically used. In the interlayer expansion of the layered zeolite precursor RUB-36, an Fe salt instead of a silylating agent was used to fill up the linking sites in between the layers. The obtained material showed a shift of the first XRD reflection similar to that of RUB-36 interlayer expanded with dichlorodimethylsilane, indicating an increase in interlayer distance. Diffuse reflectance UV-vis spectra and EPR characterization proved the incorporation of isolated Fe sites. Using FTIR spectroscopy with pyridine and acetonitrile as probe molecules, it was found that the incorporation of Fe results in an increase in Lewis acidity. The material was successfully used as a catalyst in the acylation of anisole with acetic anhydride and in the alkylation of toluene with benzyl chloride. The Fe incorporation proved to be remarkably stable. In spite of the HCl production during the alkylation reaction, no leaching was observed and the catalyst could be reused after regeneration.

Bio‐Based Nitriles from the Heterogeneously Catalyzed Oxidative Decarboxylation of Amino Acids

The oxidative decarboxylation of amino acids to nitriles was achieved in aqueous solution by in situ halide oxidation using catalytic amounts of tungstate exchanged on a [Ni,Al] layered double hydroxide (LDH), NH4 Br, and H2 O2 as the terminal oxidant. Both halide oxidation and oxidative decarboxylation were facilitated by proximity effects between the reactants and the LDH catalyst. A wide range of amino acids was converted with high yields, often >90 %. The nitrile selectivity was excellent, and the system is compatible with amide, alcohol, and in particular carboxylic acid, amine, and guanidine functional groups after appropriate neutralization. This heterogeneous catalytic system was applied successfully to convert a protein-rich byproduct from the starch industry into useful bio-based N-containing chemicals.

Tunable Prussian blue analogues for the selective synthesis of propargylamines through A3 coupling

M1[Co(CN)6]2/3-type Prussian blue analogues (M1–Co PBAs) were studied as catalysts for the synthesis of propargylamines via A3 coupling of phenylacetylene, benzaldehyde and piperidine. Cu0.86Zn0.14–Co PBA was the best catalyst for the reaction by combining the high conversion obtained with Cu–Co PBA with the excellent selectivity obtained with Zn–Co PBA.