Sodalite cages

The results suggest that the sodalite cages of Y synthesized in the presence of TMA are filled by a random process the fit for two sodium ions/cage is slightly better than for three sodium ions/cage. Sodalite cage occupancy by approximately two sodium ions is consistent with many XRD studies(13). 

Figure 2.4 Building units commonly found in zeolite frameworks. From left to right, (top row) the tetrahedral primary building unit, followed by the secondary building units 4-membered ring (4MR) 6MR (second row) double 4-membered ring (D4R) D6R (bottom row) cancrinite cage (e-cage) sodalite cage (P-cage).

Figure 1 Building units in A and X zeolite structures Si04 and AIO4 tetrahedra linked by an oxygen 24 tetrahedra= sodalite unit or ex cage Sodalite unit without the oxygens, the vertices are the tetrahedral atoms Si or Al two arrangements of sodalite units cubic array=A type (the S2 site in the window is not represented)), diamond-like array=X type...

Figure C2.12.4. Typical polyhedra found in zeolites (a) sodalite cage found in sodalite, zeolite A or faujasite (b) cancrinite or a-cage found in cancrinite, erionite, offretite or gmelinite (c) the 5-ring polyhedron found in ZSM-5 and ZSM-11 (d) the large cavity of the faujasite stmcture and (e) the a-cage fonning the large cavity in zeolite A.

Figure C2.12.5. Different framework topologies based on the sodalite cage obtained through different connection patterns.

The NaCl -SOD formed during these reactions can be clearly identified by its IR spectrum, perchlorate sodalite collapse at 1050°C. From the thermo gravimetric analysis it is evident that at this temperature the entire amount of NaCl escapes. The degree of the cage filling by salt molecules can be calculated on the basis of both the oxygen and the NaCl loss. 

Figure 11. The truncated octahedron building block (also termed sodalite cage,f or p-cage ) (a) tetrahedral atoms (usually Si or Al) are located at the corners of the polygons with oxygen atoms halfway between them. Illustration of the linkage, through double four-membered rings, of two truncated octahedra (b) and the structure of zeolite-A (c).

The detection of Brpnsted acid sites, SiO(H)Al, is the most recent achievement of 170 NMR of zeolites [119-121]. High magnetic fields and double resonance techniques have allowed the observation of this important species in zeolite HY [120]. Chemical shifts of 21 and 24 ppm have been reported for zeolite HY for the Brpnsted sites in the supercage and sodalite cage, respectively [119]. Quadrupole interaction parameters are Cq = 6.0 and 6.2 MHz and r] = 1.0 and 0.9, respectively. Signal enhancement by 1H-170 cross-polarization has also permitted the detection of the acid sites in zeolite ZSM-5 [119], where they exist with lower abundance than in HY. 

T. The 170 NMR signals that are due to acid sites in supercages and sodalite cages can be resolved in the two-dimensional plot, and their MAS NMR lineshapes for fitting are obtained by extracting two slices at the corresponding chemical shifts of the proton NMR dimension. 

One difficulty with many synthetic preparations of semiconductor NCs that complicates any interpretation of NMR results is the inevitable distribution of sizes (and exact shapes or surface morphologies). Therefore attempts to make semiconductors as a sort of molecular cluster having a well-defined stoichiometry are of interest to learn potentially about size-dependent NMR parameters and other properties. One approach is to confine the semiconductor inside a template, for instance the cuboctahedral cages of the sodalite framework or other zeolite structures, which have been characterized by multinuclear NMR methods [345-347], including the mesoporous channel material MCM-41 [341, 348]. 

It is convenient to visualize zeolites in terms of secondary building units (SBUs). Several of the SBUs currently recognized by the IZA are depicted in Fig. 3 along with other useful structural units, the sodalite and pentasil cages. The sodalite unit is... 

Recent sorption studies tend to support this interpretation. Based on sorption studies on USY-zeolites, Lohse et al. (36) concluded that whole sodalite units are destroyed during the dealumination and rebuilding of the framework in USY-zeolites. Such sodalite units provide the silica necessary to fill the large number of framework vacancies left by dealumination. The consumption of whole sodalite cages leads to the formation of "secondary" pores (vide infra). 

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