Aluminosilicate zeolites discovery

Table 1.4 lists some of the major new structures reported in the 1990s. Interestingly, as organic SDAs tended to dominate discovery of new frameworks, there were no new aluminum-rich synthetic zeoUtes reported in either the 1980s or the 1990s. The new aluminosilicate structures were all high silica or pure sihca in composition. It awaited the 2000s for new aluminosilicate zeolite materials with low to medium Si/Al to be reported (see below). 

The discovery of aluminum phosphate molecular sieves has fueled the search for new sieve like materials. This search has been amply rewarded. Newsom and Vaughan [13] were able to prepare new gallosilicate phases and gallophosphates have also been prepared [14]. One of the most interesting and startling discoveries is that of zincophosphate and beryllophosphate molecular sieves [15]. They can be prepared under very mild conditions [16] and have structures which closely resemble those of aluminosilicate zeolites [16-17]. These compounds have frameworks [(Zn02)(P02)] which are isoelectronic with the aluminosilicate framework... 

A second area that will be important in the future is the continued development of MOFs and ZlFs [152]. Much as the discovery of AlP04-based materials revolutionized the catalyhc use of zeolites when only aluminosilicates were known, MOFs and ZlFs have the potential to revolutionize low temperature processes such as oxidations and organic reachons [153]. Newly discovered materials along these same lines are covalent organic frameworks, the so-called COFs [154]. These materials have similar channels to those known for MOFs and ZlFs but tend to have higher thermal stability. 

Zeolites and related aluminosilicates constitute a vital family of microporous materials with immense applications in catalysis, sorption and separation processes [1-3]. The discovery of aluminophosphates is an important landmark in the science of these materials [4], All these materials are, in general, synthesized under hydrothermal conditions by making use of template molecules [2]. The template molecules are usually organic amines and they are involved in the formation of these framework structures in more ways than one. While it is difficult to pinpoint the exact manner in which the amines participate or direct the formation of these inorganic structures, it is generally believed that their size and shape are crucial in determining the pore structure. In recent years, a variety of open-framework structures formed by divalent metal phosphates... 

In the field of transition metal catalysis, zeolites may offer opportunities for uniform active sites. With the discovery of both aluminosilicate and aluminophosphate, zeolites with a variety of transition-metal ions in tetrahedral firework positions may offer new possibilities. On the basis of existing zeolite chemistry dealing vrith aluminum hydrolysis and the formation of adsorption adducts in the zeolite pores, chemists may envision strategies aimed at the activation of tetrahedral transition metal ions, either by lattice oxide replacement or by the application of strong donor ligands. The demonstrated... 

The synthesis of zeolites can be traced back to the nineteenth century, when Jean-Baptiste Guimet was able to produce an artificial version of the highly valued and expensive natural pigment ultramarine, an aluminosilicate sodalite containing polysulfides in its cavities. For this discovery he was awarded a French national prize in 1828. In 1862 another French chemist, St Claire Deville, synthesised an analogue of levyne... 

Published information on molecular sieve science and technolpgy has grown steadily in the last 35 years. The main impetus for growth comes from the discovery of new molecular sieve compositions and structures and from the ever-growing number of practical applications of these materials, mainly in the field of catalysis. The topic of this review is limited to nonzeolite-type molecular sieves aluminosilicate molecular sieves (zeolites) are used in this paper only as reference materials. Thus, the principal molecular sieve categories discussed include metallosilicates, with the exception of aluminosilicates, and aluminophosphates. 

It is worth mentioning the recent and interesting discovery of the aluminosilicate AS-1 of topology DFT [37]. This aluminosilicate of chemical formula l(C2Hi(>N2)o.5l[AlSi02] can be synthesized with ethylenediamine as the OSDA only in fluoride media. The role of the fluoride ions is here rather tricky but in this case the addition of HF favours the diprotonation of the ethylenediamine molecules. AS-1 opens new prospects about the use of amines in fluoride media for the preparation of novel low-silica zeolites. 

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