CARBOGENIC MOLECULAR-SIEVES - SYNTHESIS, PROPERTIES AND APPLICATIONS

Carbogenic molecular sieves (CMS) are microporous, high-carbon solids. Because of their microporosity, they share with zeolites the ability to separate molecules on the basis of size and shape. For example, nitrogen is produced from air by pressure swing adsorption over packed beds of CMS. Other shape-selective separations also can be accomplished over CMS. Despite these apparent similarities CMS are quite different from zeolites. Instead of being crystalline, they are globally amorphous having no long-range order. Despite their disorder the microporosity can be controlled through choice of precursor, additives, and thermal history. Highly variable surface chemistries-acidic, basic, neutral, and free radical-also set CMS apart from zeolites. Here the properties of CMS are reviewed in detail. Synthesis properties and applications, both separative and catalytic, are covered. Finally, microstructural features of CMS are put in context with recognized features of other carbon materials which feature minimal surfaces with high local curvature.