The concept of organic zeolite and its practical uses
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LIPKOWSKI, Janusz. The concept of organic zeolite and its practical uses. In: Physical Methods in Coordination and Supramolecular Chemistry, 8-9 octombrie 2015, Chişinău. Chisinau, Republic of Moldova: 2015, XVIII, p. 10.
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Physical Methods in Coordination and Supramolecular Chemistry
XVIII, 2015
Conferința ""Physical Methods in Coordination and Supramolecular Chemistry""
Chişinău, Moldova, 8-9 octombrie 2015

The concept of organic zeolite and its practical uses


Pag. 10-10

Lipkowski Janusz
 
Institute of Physical Chemistry of the Polish Academy of Sciences, Polonia
 
Disponibil în IBN: 17 aprilie 2020


Rezumat

The term organic zeolites has been originally introduced to chemical literature in early 1970ths by R.M. Barrer, to describe molecular crystals having open structures, able to reversibly absorb and desorb organic species with relatively weak, if any, sorption of water or other hydrophilic molecules. The compound studied by the Authors cited above was Co(NCS)2(4-methylpyridine)4, one of the formerly studied series of, reportedly, clathrate forming coordination complexes. The reversible sorption property of the compounds have been the basis for their use as stationary phases in clathrate chromatography and, in particular, as the sorbent useful for separation of isotopomers. Basic physicochemical information of these compounds has been summarized in review chapters [1]. A characteristic feature of the organic zeolite structures, when compared to classical ‘inorganic’ zeolites based on aluminosilicates, is their relatively weak intermolecular bonding, both guest-host and host-host. The latter is the reason for significant flexibility of the host crystal structure which changes its parameters upon guest absorption, desorption or exchange. The importance of the concept of organic zeolites is presently seen in the relatively new field, namely in Metal Organic Framework structures. Porous compounds of fantastic sorption capacities have been reported in the literature and the field is developing remarkably. Typically the papers are limited to basic characteristic of the product: synthesis and structure, with particular emphasis on its porosity. It is well known that the porosity depends on the presence of the guest species and, in particular, it vanishes upon guest desorption. On the other hand, the properties of the materials derived from MOFs are an interesting function of collective guest-host phenomena, including lattice dynamics [3]. In principle, an organic zeolite structure is formed as the result of supramolecular aggregation of any substrate having a hydrophobic or amphiphilic character. A special, curious example is an organic zeolite formed by water molecules which encapsulate organic guest species in such a way that all hydrophilic functions of water ,molecules are directed outwards the intermolecular space left for the guest component. In general, organic zeolite behavior may be observed on a large variety of supramolecular materials, including solvates of macrocyclic compounds. In the paper solvation of cyclodextrins and synthetic macrocycles will be used as the convenient example, based on brand new, mostly yet unpublished large structures of heavily solvated cyclodextrin complexes in the solid state.