Periodic Mesoporous Organosilica

Periodic Mesoporous Organosilica
Author: Steven Edward Dickson
Publisher:
Total Pages: 458
Release: 2011
Genre:
ISBN:
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There is currently a great interest in the field of porous organosilica materials because of the high surface areas (> 1000 m2/g) and narrow pore size distributions which are beneficial for applications such as chromatography, chiral catalysis, sensing or selective adsorption. Periodic mesoporous organosilicas (PMOs) represent an interesting class of hybrid silica materials because of the wide variety of bridging organic groups which can be incorporated within the precursors [(OR)3Si-R-Si(OR)3] giving rise to materials with exceptional properties. We have synthesized and characterized various aromatic PMOs composed of supporting structural monomers (phenylene- or biphenylenebridged) and functional stilbene monomers (cis and trans) (1, 2). The effect of the different synthetic procedures and varying amounts of functional stilbene monomer on the properties of the materials was examined. The functional transstilbene component was determined to be well distributed in a phenylene-bridged PMO using P123 as a pore template from TEM techniques with Os staining. The trans-stilbene linkers were completely transformed to aryl aldehydes through ozonolysis with dimethylsulfide workup. Further transformation of the carbonyl functionality to an aryl imine showed a moderate level of success. Enantiomeric forms of a novel, chiral PMO precursor (CM) were synthesized and incorporated into biphenylene-bridged PMOs. Under basic pH conditions templated with C18TMACl, although very low levels of CM are incorporated, enantiomeric forms of chiral, porous materials are obtained as was verified by distinct mirror-image circular dichroism spectra. Powder XRD patterns suggest that a tightly packed asymmetric biphenylene arrangement may be necessary for the optical activity. Preliminary results using these materials as a chiral chromatographic phase are promising. Finally, a thin film morphology of an ethane-bridged PMO incorporating a thiol ligand, (3-mercaptopropyl)trimethoxysilane, was prepared on a fibre optic cable and used as a component in a heavy-metal sensing application.

I. PROGRESS IN DIRECTED Ortho METALATION II. II. GENERATING CHIRALITY IN PERIODIC MESOPOROUS ORGANOSILICA.

I. PROGRESS IN DIRECTED Ortho METALATION II. II. GENERATING CHIRALITY IN PERIODIC MESOPOROUS ORGANOSILICA.
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Total Pages:
Release: 2009
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ISBN:
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Chapter 1 constitutes a review of current methods of aromatic substitution focusing on Directed ortho Metalation (DoM) and Directed remote Metalation (DreM). The field of mesoporous silica is reviewed in Chapter 2, focusing on the preparation, characterization, and application of mesoporous silicates. Chapter 3 presents an introduction of phosphorus based Directed Metalation Groups (DMGs). The development of the directed ortho metalation (DoM) reaction of the tetraethyl phosphorodiamidate DMG is described. In addition to being one of the most powerful DMGs, migration of the OPO(NEt2)2 group to the ortho and remote positions is demonstrated, constituting new reactions as well as affording new organophosphorus compounds. Attempts to improve the synthetic utility of the DMG led to the discovery and optimization of a two new nickel-catalyzed cross coupling reactions, which is described in Chapter 4. Both the OPO(NEt2)2 and OCONEt2 DMGs are demonstrated to undergo cross coupling reactions with aryl boronic acids. By means of DoM and cross coupling tactics, the concise synthesis of a chiral binaphthol bridged silasesquioxane is described. Chapter 5 explores new methods to prepare chiral periodic mesoporous organosilica (PMO) materials using this monomer. PMOs are prepared by the co-condensation of a relatively small amount of chiral binaphthyl dopant which acts to twist the bulk prochiral biphenylene framework.

Periodic Mesoporous Organosilicas

Periodic Mesoporous Organosilicas
Author: Chang-Sik Ha
Publisher: Springer
Total Pages: 333
Release: 2018-11-07
Genre: Technology & Engineering
ISBN: 9811329591
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This book provides a comprehensive overview of the fundamental properties, preparation routes and applications of a novel class of organic–inorganic nanocomposites known as periodic mesoporous organosilicas (PMOs). Mesoporous silicas are amorphous inorganic materials which have silicon and oxygen atoms in their framework with pore size ranging from 2 to 50 nm. They can be synthesized from surfactants as templates for the polycondensation of various silicon sources such as tetraalkoxysilane. In general, mesoporous silica materials possess high surface areas, tunable pore diameters, high pore volumes and well uniformly organized porosity. The stable chemical property and the variable ability for chemical modification makes them ideal for many applications such as drug carrier, sensor, separation, catalyst, and adsorbent. Among such mesoporous silicas, in 1999, three groups in Canada, Germany, and Japan independently developed a novel class of organic–inorganic nanocomposites known as periodic mesoporous organosilicas (PMOs). The organic functional groups in the frameworks of these solids allow tuning of their surface properties and modification of the bulk properties of the material. The book discusses the properties of PMOs, their preparation, different functionalities and morphology, before going on to applications in fields such as catalysis, drug delivery, sensing, optics, electronic devices, environmental applications (gas sensing and gas adsorption), biomolecule adsorption and chromatography. The book provides fundamental understanding of PMOs and their advanced applications for general materials chemists and is an excellent guide to these promising novel materials for graduate students majoring in chemical engineering, chemistry, polymer science and materials science and engineering.