Inorganic-organic hybrid monoliths

ORMOSIL Inorganic-Organic Hybrid Monoliths in One Phase... 

There are some excellent review articles on different aspects of mesostructured materials, such as synthesis, properties, and applications. " Extensive research effort has been devoted to the exploitation of new phases (lamellar, cubic, hexagonal structures), expansion of the pore sizes (about 2-50 nm are accessible), and variable framework compositions (from pure silica, through mixed metal oxides to purely metal oxide-based frameworks, and inorganic-organic hybrid mesostructures). Another research focus is on the formation of mesostructured materials in other morphologies than powders, e.g. monolithic materials and films, which are required for a variety of applications including, but not limited to, sensors (based on piezoelectric mass balances or surface acoustic wave devices), catalyst supports, (size- and shape-selective) filtration membranes or (opto)electronic devices. The current article is focused... 

Figure 10.1 Types of silica-based sol-gel monoliths differing in porosity, (a) Aerogels, highly porous monoliths, (b) Xerogel, semiporous monoliths, (c) Inorganic-organic hybrid, nonporous monoliths.

Nanoporous carbon with narrow pore-size distribution can be prepared directly via a one-step nanocasting technique by carbonization of cyclodextrin-silica organic-inorganic hybrid composite.[260] The method consists of preparing a cyclodextrin-templated silica mesophase via soft chemistry, followed by direct carbonization of the occluded cyclodextrins. The nanocasting procedure provides granules (in millimeter scale) or monoliths (in centimeter scale). Cyclodextrins can be employed not only as structuredirecting templates but also as carriers for metal nanoparticle precursors. 

Hybrid metal oxide/polymer monoliths are formed when sol-gel reactions are performed within the pore system of the organic gel [7, 8]. The alcohol soaked polymer gel is simply placed in the liquid precursor and then into an al-cohol/H20 solution for hydrolysis and condensation, which gives an amorphous metal oxide layer on the polymer surface. Heating the hybrid at 450 °C results in removal of the organic template and crystallization of the inorganic material. 

Individual submicron entities can be cast to form monolithic structures with voids that maintain the initial organic shape (as was discussed above), or they can be coated to give individual hybrid entities that form hollow inorganic structures on removal of the template. The particles, tubes, and crystals are generally dispersed in solution for templating. 

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