Novel SDAs

Using this technique, Lewis and coworkers were able to rationalize the efficacy of observed SDAs that have been employed to direct for known zeolite phases and also to predict novel SDAs to direct for the known molecular sieves. In particular, they were able to identify SDA molecules suitable for the synthesis of the previously identified phases LEV, CHA, MFI, and EUO [38, 39]. Although the technique is effective in these cases it has not been employed to generate a novel zeolite topology. 

Construction of D4R-containing Zeolites by using Ge as a Silica Substituent Recently, the use of germanium as a silica substituent coupled with the use of novel SDAs by Corma et al. has led to the discovery of many new D4R-containing zeolite... 

SDAs are featured for their structure diversity and controllability to meet the objective of designed synthesis of zeolites with specific structures. Studies show that SDAs with proper shape, polarity, charges, and flexibility are the keys to achieve the design of novel zeolite structures [63]. Nowadays, many zeolite structures have been synthesized by using novel SDAs. Besides, hierarchical zeolites can be synthesized with bifunctional templates. Some representative works will be discussed later. 

The crystal structure of the novel chabazite-type material CAL-4 displays a layered organization of the SDAs, which may be responsible for an unusual plate-like particle shape. It is predicted that the morphology of the crystallites can be designed by choosing suitable SDAs. 

The initial success of the effort to design the size and shape of the SDA molecules to preclude the formation of the clathrate or 1-D materials resulted from a derivative of the camphor-type molecule (Fig. 3.5) that led to the crystallization of the novel, open-framework zeolites SSZ-35 (STF) and SSZ-36 (ITE/RTH). Subsequently, numerous other zeolite structure-directing molecules were discovered using this design strategy and are presented in reference [41],... 

Organometallics as a novel class of SDAs also offer the chance to generate new framework topologies, and this has in fact been accomplished in one case (see below) In particular, it might also be possible to discover the "Holy Grail" of synthetic zeolite chemistry, namely, the preparation of a chiral zeotype structure by using metal complexes as SDAs with a chiral shape. 

Zeolites have micropores with ordered size and solid acidity, and there has been growing interest in the application of zeolites as catalysts as well as molecular sieves. We investigated the synthesis of novel zeolites by using ammonium salts as structure-directing agents (SDAs) [1, 2]. 

Ikeda and coworkers synthesized a novel silicate zeolite CDS-1 (CDO) with a cylindrically double saw-edged framework in 2004 [114]. CDS-1 was converted by dehydration-condensation between the layers of pentagonal cylinder-layered silicate (PLS-1). Then in 2008, Okubo and coworkers synthesized novel silicate sodalite (SOD) by topotactic conversion [119]. Another example is shown by Gies and coworkers with the preparation of silicate zeolite RUB-41 (RRO) [109]. By studying the synthesis of hydrous-layered silicates carefully, they used dimethyldipropylammonium hydroxide as the organic SDA to synthesize the layered silicate precursor (RUB-39), and RUB-41 was synthesized after the calcination of RUB-39. 

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