Zeolites organic

Aoyama Y. Functional Organic Zeolite Analogs Top. Curr. Chem. 1998 198 131-161... 

MOFs can be considered as organic zeolite analogs, as their pore architectures are often reminiscent of those of zeolites a comparison of the physical properties of a series of MOFs and of zeolite NaY has been provided in Table 4.1. Although such coordinative bonds are obviously weaker than the strong covalent Si-O and Al-O bonds in zeolites, the stability of MOF lattices is remarkable, especially when their mainly organic composition is taken into account. Thermal decomposition generally does not start at temperatures below 300 °C [3, 21], and, in some cases. 

It is a challenge to couple the antenna systems to a device (e.g., a semiconductor). It has already been shown that it is possible to prepare organized zeolite monolayers on flat surfaces [78, 79]. For coupling, the interface between the chromophore loaded zeolite L antenna systems and the semiconductor becomes very important. Stopcock molecules are expected to function as a bridge between the chromophores in the zeolite L channels and the device surface, which will open a whole new exciting research area. The first successful experiments with slopcock modified crystals have been reported recently [80]. 

Boyd GE, Adamson AW, Myers LS (1947) The exchange adsorption of ions from aqueous solutions by organic zeolites II. Kinetics. J Am Chem Soc 69 2836-2848 Brindley GW, MacEwan DMC (1953) Structural aspects of the mineralogy of clays and related silicates. In Green AT, Stewart GH (eds) Ceramics—A Symposium. The British Ceramic Society, Stoke-on-Trent UK, pp 15-59... 

Dendrimer 23 has been viewed as a potential organic zeolite because it could serve as a reaction chamber for small guest molecules. The three-dimensional branched structures of 22 and 23, as revealed by computer models, are shown in Figures 3a and 3b, respectively. ... 

Porous materials such as organic zeolites discussed in Section 8.4 are vigorously studied since they often exhibit catalytic activity [122]. An interesting type of zeolite materials is obtained by tucking chiral amines inside pores of a commercially available zeolite. Such an approach allowed Ramamurthy s group to enhance stereoselectivity of a photochemical reaction [122b]. 

Numerous applications of organic zeolites have been proposed. In the future they could serve as catalytic sites and miniature reaction chambers as well as storage compartments and stationary chromatographic phases to be used for the... 

Hertzsch, T., Budde, F., Weber, E., Hulliger, J., Supramolecular-wire confinement of I2 molecules in channels of the organic zeolite tris(o-phenylenedioxy)cyclotriphosphazene. Angew. Chem., Int. Ed. 2002, 41, 2281-2284. 

Multiple hydrogen bonding interactions in tetrahedral building blocks have been employed by the group of Wuest to produce a remarkable tailored porous zeolite mimic, dubbed an organic zeolite because it does not contain any inorganic components at all.104 The pore-forming material is based on... 

Robust inorganic porous networks such as zeolites are of tremendous industrial interest in separation, storage and catalysis. As a result they have stimulated the preparation of a wider range of organic zeolites that aim to mimic their porous and robust properties while allowing more extensive synthetic tenability. 

The very last example here refers to the, so-called, organic zeolites. There are several structures which belong to this class of inclusion compounds and their physicochemical properties are remarkable, being of particular interest to separation science. An example of crystal structure of the compounds is given in Fig. 11.10 [9]. 

Fig. II.10 Crystal structure of organic zeolite formed by Ni(NCS)2(4-methylpyridine)4. Yellow spheres represent symbolically the empty space available for guest species...

Fig. 11.11 Flexibility of the organic zeolite structure (cf. Fig. 11.10 above) expressed in terms of molar volume of the empty space (calculated as the difference between the molar volume of the solid and the volume of the host) at equilibrium with mixed solvents acetone/4-methylpyridine and ethanol/4-methylpyridine...

A variety of guests may be absorbed in organic zeolite and just very simple examples of the resulted structures are solved by X-ray diffraction. This is due to fuzzy electron density maps in the guest region when it is a chemical mixture or it is orientationally disordered. A rare example of the two-component guest zeolite structure is given below [11] (Fig. 11.12). 

Fig. 11.12 A section drawing displaying the mutual positions of the host and guest species in organic zeolite (cf. Fig. 11.10). The guest is a two-component mixture of ethanol (ET) and benzene (B)...

D channels to run through the structure. This structure is particularly relevant since it represents the first reported example of a compound that might be regarded as a metal-organic zeolite, i.e. the structure is porous and stable to loss of guest.25 The bilayer architecture has also been reported for systems using l,2-bis(4,-pyridyl)ethane. 

Recently Yaghi and co-workers reported a coordination network based on trimesic acid and Co(n) which retained its porous structure upon the removal of solvent molecules and selectively absorbs aromatic guests. Also, Fujita, Ogura and co-workers have demonstrated that cyanosilation of aldehydes can be performed in the microchaimels of a two-dimensional square material composed of cadmium(II) and 4,4 -bipytidine. From the examples described above, it is quite apparent that organic zeolites are more of a reality than a fantasy. What is the future that await these porous compounds with zeolitic behavior ... 

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