Building unit

The traditional definition of a zeolite refers to microporous, crystalline, hydrated aluminosilicates with a tliree-dimensional framework consisting of comer-linked SiO or AlO tetrahedra, although today the definition is used in a much broader sense, comprising microporous crystalline solids containing a variety of elements as tetrahedral building units. The aluminosilicate-based zeolites are represented by the empirical fonmila... 

Figure C2.12.3. Secondary building units in zeolites. Each comer represents a T-atom (Si, Al) while tire connecting lines represent oxygen bridges witli tire oxygen atom in tire middle.

Fig. 1. Methods for representing SiO and AlO tetrahedra by means of (a) baH-and-stick model, (b) soHd tetrahedron, (c) skeletal tetrahedron, and (d) spare-filling of packed spheres (1). (e) Linking of four tetrahedra in a four-membered ring, (f) Secondary building unit called tmncated octahedron as...

The chemical industry was the first to utilize catalytic oxidation extensively for emission control, building units capable of treating up to 50 m /s (100,000 scfm) of exhaust gas containing VOCs. Catalytic systems accounted for roughly one-fourth of the 200 million market for VOC control systems in 1992, and over one thousand catalytic oxidization devices were in place by the end of that year (5). 

Poly(L-malic acid) denotes a family of polyesters derived from L-malic acid as the building unit. By chemical synthesis, three kinds of poly(L-malic acid) have been obtained, depending on the molecular position of the ester bond the a-type(I) [1], the j8-type(II) [2], and the a,j8-mixed-type(III) [3). 

The expressions in parentheses may be varied independently. These correspond to the Schottky building units. In the latest notation, interstitials are indicated by the chemical elements without any subscript, and vacancies are indicated by the missing chemical element between two vertical lines. Equations (5) or (6) then read ... 

Thermodynamic equilibrium laws are applicable to the Schottky building units. However, there is a loss in intuition. In view of that conflict, the DSEs [11] make use of Kroger-Vink structural elements with the meaning of Schottky building units. This conversion is easily achieved by omitting all ideal lattice elements such as M on M sites, M M, and interstitial vacancies, V . This reads, for the example of Eqs. (5H7),... 

The use of FOSS polyhedra as models for silica surfaces or as secondary building units in inorganic materials such as zeolites or other porous solids is likely to increase rapidly as more is understood about the mechanisms by which the polyhedra may be constructed. It will be of particular interest to see if the larger structures such as TeoHeo or T240H240 or their derivatives (Section VII.C) and analogous to carbon structures such as Cgo or nanotubes, can be prepared. 

Figure 4.2 A number of secondary building units encountered in MOFs (a) the paddlewheel complex (b) the trioctahedral bipyramidal complex and (c) the infinite chain of octahedra. The squares and octahedra represent the metals within their...

Fig. 13.1 The structure of CS5I113AS4 contains both layers and chains of [InsAsJ shown in (a) and (b), respectively. Shown in boxes is the same building unit of the chains and the layers, i.e., a dimer of semicubanes of ln3As4.

A close analysis of the chlorine-centered ClA6.nMn octahedral SBU (secondary building unit) has revealed that the acentricity of the bulk lattice may be introduced via cation substitution. The di-cation substitution (n=2) in ClNas... 

As described earlier, we classify dendritic poiyrotaxanes in which rotaxane building units grow like a dendrimer, as Type III rotaxane dendrimers. Depending on whether ring components are located on the branches or at the branching points. Type III rotaxane dendrimers are further classified as 111-A and 111-B, respectively. 

Molybdenum trioxide has a layered structure with orthorhombic symetry [16] (a=3.963, b=ll855, c=3.696 A), this structure consists of double layer sheets parallel to the (010) cleavage plane. The building unit is a distorted M0O6 octahedron, with Mo-0 distances 1.67, 1.73, 1.95 (twice), 2.25 and 2.33 A (Fig.l)... 

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