Porous carbons confinement

Since the discovery of ordered mesoporous materials, researchers have explored many possible applications that can take advantage of the unique compositional or structural features of mesoporous materials. In addition to apphcations in traditional areas such as catalysis, separation, and ion exchange, new applications that might involve mesoporous materials include stationary phases in HPLC, bio and macromolecular separations, low dielectric constant materials, enzyme immobilization, optical host materials, templates for fabrication of porous carbons, and reactions in confined enviromnents. 

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. 

Via confined space synthesis with porous carbon as inert support material, synthesis of nanosized zeohte crystals of several topologies is possible and their recovery via controlled pyrolysis of the carbon becomes feasible [155]. In the 45-nm carbon black pores nanocrystals of ZSM-5 (MFI) of about the same size were obtained. The method is of general utiUty, as it seems possible to make nanosized zeohtes of Beta zeolite X and Y and L (LTL), which can be easily washed, ion exchanged and finally isolated via calcination [156]. 

Lee KT et al (2008) Liquid gallium electrode confined in porous carbon matrix as anode for lithium secondary batteries. Electrochem Solid-State Lett 1LA21-A124... 

Liquid-vapor phase transitions of confined fluids were extensively studied both by experimental and computer simulation methods. In experiments, the phase transitions of confined fluids appear as a rapid change in the mass adsorbed along adsorption isotherms, isochores, and isobars or as heat capacity peaks, maxima in light scattering intensity, etc. (see Refs. [28, 278] for review). A sharp vapor-liquid phase transition was experimentally observed in various porous media ordered mesoporous sifica materials, which contain non-interconnected uniform cylindrical pores with radii Rp from 10 A to more than 110 A [279-287], porous glasses that contain interconnected cylindrical pores with pore radii of about 10 to 10 A [288-293], silica aerogels with disordered structure and wide distribution of pore sizes from 10 to 10" A [294-297], porous carbon [288], carbon nanotubes [298], etc. 

IUPAC classification, mesoporous materials are defined as porous materials with diameters in the range 2-50 nm, which is rather dose to the dimensions of functional biomolecules such as proteins. Therefore, unexplored phenomena and functions could be observed for biomolecules confined in mesopore channels due to their restricted motion and orientation. In this chapter, we briefly introduce recent developments on the immobilization of biomolecules in mesoporous media, where the use of mesoporous silica and mesoporous carbon are mainly discussed. 

In purification filters for purifying liquids or gases, sometimes a loose bed of grains of an adsorbent material, such as activated carbon, is located between two porous walls which confine the grains. Since there is no cohesion within the granular material, the flow and filter use period are difficult to control. 

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