Frameworks types

Crystal chemistry ofTa and Nb fluorides - compounds with framework type structures 101... 

Framework-type structure Coordination-type structure... 

Figure 10.1 Framework types of some well-known zeolites with their specific pore size and pore network dimensions [5].

We have observed large variations in the sorption capacities of zeolite samples characterized by (ID) channel systems, as for instance AFI (AIPO4-5 zeolite) and MTW (ZSM-12 zeolite) architectural framework types. Indeed, for such unconnected micropore networks, point defects or chemisorbed impurities can annihilate a huge number of sorption sites. Detailed analysis, by neutron diffraction of the structural properties of the sorbed phase / host zeolite system, has pointed out clear evidence of closed porosity existence. Percentage of such an enclosed porosity has been determined. 

Ch. Baerlocher, W. M. Meier and D. H. Olson, Atlas of Zeolite Framework Types, Elsevier, Amsterdam, (2001) 184. 

Porous materials are elassified into three different categories based on the size of pores rpore, that is, microporous for rpore < 20 A, mesoporous for 20 A< Tpore < 500 A, and macroporous for rpote > 500 A. Here I will discuss micro- and meso-porous materials. Microporous crystals (hereafter called zeolites) with more than 150 different framework-type stmctures have been reported. 

The IZA has several established Commissions. The Structure Commission formed in 1977 has published four editions of the Atlas of Zeolite Structure Types (1978, 1987, 1992, 1996) and two subsequent editions in the Atlas of Zeolite Framework Types (2001, 2007). An up-to-date version is maintained on the World Wide Web at the IZA Structure Commission web site (http //www.iza-structure.org). Subsequently commissions were established in catalysis (1998), synthesis (1992), ordered mesoporous materials (2001) and natural zeolites (2001). The synthesis commission published a volume, Verified Syntheses of Zeolitic Materials , in 1998, with a second revised edition in 2001 (http //www.iza-structure.org). 

B.A., and Wilson, S.T. (2004) UZM-4 a stable Si-rich form of the BPH framework type, in Recent Advances in the Science and Technology of Zeolites and Related Materials, Proceedings of the 14th International Zeolite Conference (eds E.W.J. van Steen, l.M. Claeys, LH. Callanan, and C.T. O Connor), Stud. 

Ref [3]]) found in the MOR framework type, (f) Complex pentasil chain (designated kgl by Smith [Ref [3]]) found in the MFI framework type. The nodes are tetrahedrally coordinated atoms such as Si or Al. Bridging oxygen atoms have been left out for clarity. 

Figure 2.5 Cumulative number of framework types by year approved by the IZA Structure Commission and given a three letter code (assignment of dates before 1992 is uncertain).

Knowing the framework type of a material, the size of molecules that can be adsorbed can be estimated. Kinetic diameters for various molecules [5-9] are given in Table 2.2. Thus neopentane (kinetic diameter of 0.62 nm) is expected to be adsorbed by NaX zeolite (FAU structure type) which has channels defined by 12-... 

Figure 2.6 Eight-ring pore in LTA framework types. O-atoms and T-atoms are represented are large (0.135nm radius) and small (0.026 nm radius) spheres respestively. The...

Table 2.3 Framework types with larger than 12-rings.

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