Framework topologies

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

Figure C2.12.6. Framework topology of ZSM-5. The 5-ring polyhedron is connected into chains which fonn the ZSM-5 stmcture with the 10-membered openings of the linear channels.

Figure 7. Schematic representations of a ) (3D) b) (2D ) and c) (ID ) porous framework topologies.

The >24 structures of AlP04-based molecular sieves reported to date include zeolite topological analogs and a large number of novel structures. The major structures are shown in Table 1.3. They include 15 novel structures as well as seven structures with framework topologies related to those found in the zeolites... 

In the metal aluminophosphate (MeAPO) family the framework composition contains metal, aluminum and phosphorus [27]. The metal (Me) species include the divalent forms of Co, Fe, Mg, Mn and Zn and trivalent Fe. As in the case of SAPO, the MeAPOs exhibit both structural diversity and even more extensive composihonal variation. Seventeen microporous structures have been reported, 11 of these never before observed in zeoUtes. Structure types crystallized in the MeAPO family include framework topologies related to the zeolites, for example, -34 (CHA) and -35 (LEV), and to the AIPO4S, e.g., -5 and -11, as well as novel structures, e.g., -36 (O.Snm pore) and -39 (0.4nm pore). The MeAPOs represent the first demonstrated incorporation of divalent elements into microporous frameworks. 

The MeAPSO family further extends the structural diversity and compositional variation found in the SAPO and MeAPO molecular sieves. These quaternary frameworks have Me, Al, P and Si as framework species [27]. The MeAPSO structure types include framework topologies observed in the binary AIPO4 and ternary (SAPO, MeAPO) compositional systems and the novel structure -46 with a 0.7 nm pore. The structure of -46 has been determined [34]. 

Tschortnerite (TSC) surely is the most remarkable novel zeohte mineral discovered [67]. Its unique framework topology contains five different cages D-6Rs, D-8Rs, sodahte cages, truncated cubo-octahedra and a unique 96-membered cage. Cu-containmg clusters are encapsulated within the truncated cubo-octahedra. The pore structure is three-dimensional with 8R charmels, and the framework density of 12.2 is among the lowest known for zeolites. The framework is alumina-rich with Si/Al = 1, unusual for zeohte minerals. 

Pawlesa, J., Bejblova, M., Sommer, L, Bouzga, A.M., Stocker, M., and Cejka, J. (2007) Synthesis, modification and characterization of MWW framework topology materials. Stud. Surf. Sci. 

Bu, X., Gier, T.E., Feng, P., and Stucky, G.D. (1998) Cobalt phosphate based zeolite structures with the edingtonite framework topology. Chem. Mater., 10, 2546-2551. 

Of the zeolites reported since 1969, most represent compositional variants of previously known framework structure types with respect to cation, framework, and intercalated salt compositions. Zeolite species that may represent new types of framework topologies include Losod (18) ZSM-5, 8, and 11 (8, 10, 11) ZSM-10 (12) Ba-N and Ba-T (20) and Li,Na-0 (24). Zeolites Z-21 (82) and Na-V (29) are not included because of their apparent structural relationship to zeolite N. Except for Losod, no structural studies have been reported. 

This fifth edition of the Zeolite Powder Pattern Collection contains calculated patterns of 226 zeolite materials representing 176 framework topologies - an increase of 43 new topologies since the fourth edition in 2001. 

Materials with the same framework type code (i.e. framework topology) may have very different diffraction patterns, so for some framework type codes several different reference materials have been included. Examples listed under FAU, GIS, MFI and NAT illustrate the extent of the differences observed in the diffraction patterns of materials with identical framework topologies but variations in composition and/or symmetry. 

Each species is also denoted by a three-letter structure code that describes the framework topology (connectivity, channel dimensionality etc). Examples are given in Table 9.1 common structures of some representative zeolites are shown in Figure 9.6. 

Table 9.1 Characteristics of some common zeolite framework topologies.

Table II gives the unit cell composition of the 10 of our as synthesized samples for which an accurate analysis was possible. Also are included and adapted 3 other Nu-10 samples for which an analysis was available in the literature (samples 14, 15, 18). We also included the composition of silica-ZSM-22, another zeolite possessing the same framework topology as Nu-10 (12), that was synthesized in presence of diethylamine (DA) under veiy particular conditions (12).

Zeolite Nu-10 was demonstrated to possess the identical framework topology than zeolites ZSM-22 (55), Theta-1 (57), KZ-2 (38) and ISI-1 (59). The complete crystal structure of Theta-1, ZSM-22 and of its Si end-member was elucidated (Table m). 

On these grounds, it is concluded that the as-synthesized Na-ZSM-5 possesses an isostructure with TPA-ZSM-5 but differs in framework topology from the so-called ZSM-8 structure. 

The intensity ratio of the 41.2 ppm line to the sum of the lines between -11 and -24 ppm is 1.07 0.05. This indicates that within experimental error the proportion of Al(IV) to Al(VI) is fixed by the framework topology and does not change with the incorporation of Si. 

The reaction of zeolites with an aqueous fluorosilicate solution under relatively mild conditions has been shown to yield zeolites with silicon enriched frameworks which are essentially free of structural defects (1). As a result of the treatment, the framework topologies of the respective zeolites are relatively unchanged, but the zeolite compositions which are produced either do not occur naturally or are not synthesized directly. The fluorosi1icate treatment process has been termed "Secondary Synthesis". 

ZSM-23 is a medium pore high silica zeolite with interesting catalytic and adsorptive properties (1-5). Recently, its framework topology was shown to have orthorhombic symmetry (Pmmn) with unit cell parameters of a = 0.501 nm, b = 2.152 nm and c = 1.113 nm. The pore structure of ZSM-23 consists of linear, non-interpenetrating channels with teardrop shaped openings of ca. 0.45 x 0.56 nm (6). It was proposed to denote this framework topology as MTT (Mobil-twenty-three) (6). Based on a comparison of X-ray powder data, it was suggested that two other zeolites, viz. KZ-1 ( 7) and ISI-4 (8j also possess the MTT framework (6). 

Recently Briscoe et al. (2) described the framework topology of zeolite EU-1. It consists of a unidimensional 10-membered ring channel system with side pockets formed at regular intervals off the channels. The unit cell contains 112-T atoms and the framework symmetry is Cmma. 

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