Periodic mesoporous silica-based materials

CHARACTERIZATION OF PERIODIC MESOPOROUS SILICA-BASED MATERIALS... 

Sayari, A. Hamoudi, S. 2001. Periodic mesoporous silica-based organic—inorganic nanocomposite materials. Chem. Mater. 13 3151-3168. 

A. Sayari and S. Hamoudi, Periodic Mesoporous Silica-Based Organic-Inorganic Nanocomposite Materials, Chem. Mater., 2001, 13, 3151. 

Many of the non-silica compositions showed problems with the stability and quality of the structure. Efforts to address these issues have been on going and quite successful in some cases such as all-alumina compositions (see below). Silica-based materials remain dominant as the most versatile and best quality molecular sieves (structure and stability) available by a facile synthesis. These attributes, especially the convenient synthesis made mesoporous silicate attractive for post-synthesis functionalization with other elements as well as organic moieties with active groups/ccnters. Recently the compositional diversity has been extended further to include both silica and organic moieties within the framework. The new class is referred to as periodic mesoporous organosilicas (PMOs). The synthesis involves surfactant-assisted assembly by hydrolysis of organo-silicon compounds. Additional discussion of the PMOs is presented below. 

Based on these findings, calixarene materials have been synthesized for entrapment of NOx gases. Specifically, calix-silica gel (39) (73) and caUx[4]-arene-based periodic mesoporous silica (40) (75) were prepared (Fig. 16). In the NO2 entrapment experiments, a stream of the gas was passed through columns... 

The so-called template-based technique has been found to be particularly suitable for the synthesis of carbons whose porosity is not only uniform in size and shape, but also periodically ordered in some cases. In this approach, the porous carbon is prepared through infiltration of an organic precursor into the nanochannels of an appropriate inorganic material (the template), followed by carbonization and then liberation of the resultant carbon from the template. Different nanospaces in templates have been used to confine the carbon precursors. The first templates used included, e.g., silica gel or porous glass [84,85], layered clays such as montmorillonite ortaeniolite [86,87], or pillared clays [88-90]. Several detailed reviews on this topic have been published [75,91-95] that cover the areas of microporous and, especially, mesoporous solids. Here, some illustrative examples will he presented in some detail rather than reviewing systematically the literature. 

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