Metal post-synthetic modification

Post-synthetic modification methods (route A in Figure 36.2) rely on the presence of silanol groups on the inside of the pore walls. The simplest type of post-synthetic modification is the hydrophobization of the calcined mesoporous materials by reaction with alkylchloro- or alkylalkoxy-silanes, - " but functional groups and metal complexes can also be attached. - " ... 

Post-synthetic Modification Metallation and Pore-size Modification... 

In contrast to these post-synthetic modifications, it is also possible to functionalize the pore walls directly during the synthesis, as was first shown by Mann and co-workers [7,8] and Stucky and coworkers [9], who used trialkoxysilanes R-Si(OR )3. In our approach, such R Si(OR )3 molecules substitute for part of the TEOS. After hydrolysis, they serve as additional framework components during the hydrothermally induced condensation. An essential condition for this approach is that the trialkoxysilane does not destroy the micellar arrangement of the surfactant, which gives rise to the mesostructure. In mesostructures produced in this way, the R residues should be covalently linked to the silica walls. After the synthesis, the organic surfactant molecules can be removed by extraction so that a modified mesoporous material should remain. For example, when using phenyltrimethoxysilane (PTMOS), phenyl groups may become attached to the walls of the mesopores these can be utilized for further modifications, e.g. the immobilization of metal complexes. 

Burrows AD. Post-synthetic modification of MOFs. In Llabres i Xamena FX, Gascon J, editors. Metal organic frameworks as heterogeneous catalysts. Cambridge The Royal Society of Chemistry 2013. p. 31-75. 

Metal-Organic Framework Materials covers topics describing recent advances made by top researchers in MOFs including nanoparticles and nanoscale frameworks, mesoporous frameworks, photoreactive frameworks, polyrotaxane frameworks, and even edible frameworks, as well as functionalized frameworks based on porphyrins, fluorine, and alumimun. In addition, the volume features aspects on mechanochemical synthesis and post-synthetic modification, which provide discussions on new vistas... 

Schmucker et al. reviewed the importance of chromophores in DNA functionalization. These chromophores can he DNA bases or their substitutes. The authors summarized the synthetic chemistiy published over the last ten years through which they have modified DNA with various chromophores, fluorescent probes, and metal-ion ligands by using three different approaches, i.e., replacement of DNA bases, modifications of DNA bases, and sugar modifications at the 2 -position via either the phosphoramidite chemistiy or a post-synthetic modification. These modifications could play a useful role in the development of functional nanomaterials. 

Post-synthetic modification can also be used for the synthesis of chiral MOFs via introducing chiral catalysts into the open coordination site of metal nodes of achiral MOFs [4S]. After the removal of the coordinated water molecules, two... 

Direct synthesis of metal-substituted zeolites has long been sought. However, since the post-synthesis modifications can be made under wide-ranging conditions (temperature, solvent, atmosphere, pH, etc.) far from those for the zeolite synthesis, the modifications of zeolites present us with powerful indirect methods for manipulating the properties of zeolites. Therefore, the fine-tuning of the properties of zeolites will continue to be achieved by developing various post-synthesis modification procedures as well as direct synthetic techniques. 

The change of composition of mesoporous materials can be done by direct synthesis and post-synthesis modification. Now, the composition of mesoporous materials can be extended to nonsilica oxides, phosphates, sulfides, even metals. The study of nonsilica mesoporous materials started much later than that for silica-based materials. The main reasons include the hydrolysis and condensation reactions of transition metal precursors is difficult to control the inorganic wall easily crystallizes and results in the loss of mesostructures the synthetic procedure is difficult to repeat. 

As pointed out already, free NH-sulfoximines were considered to be the most useful synthetically, because they allowed a variety of post-modifications at the sulfoximine nitrogen. Although at the outset of our studies the binding site of metals (in the sense of metal ions, metal complexes, and suchlike) was uncertain and it was difficult to predict which heteroatom of the sulfoximine (or even both) would coordinate [38, 39], we expected the sulfoximine nitrogen to play an important role in the activity and the stereoselectivity of a given catalytic system. 

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