Synthesis and Crystal Structure of As-Synthesized and Calcined Pure Silica Zeolite ITQ-12

Yang, Xiaobo; Camblor, Miguel Á.; Lee, Yong Jae; Liu, Haiming; Olson, David H.

doi:10.1021/ja0481474

Cited by 64 publications

(89 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The location of guests in 123TMI-ITW and 13DMI-ITW, found by Fourier analysis (see Supporting Information), is similar to that found in 134TMI-ITW: 8 (Figure 4, right). The center of gravity is close to the cavity center (0.55 Å) for the first orientation mentioned and is farther apart (1.12.…”

Section: ■ Experimental Sectionsupporting

confidence: 71%

“…While the three zeolites are easily recognized as belonging to the ITW framework type, it is clear that the samples prepared with 123TMI and 13DMI present four weak additional reflections that cannot be indexed in the originally reported Cm cell. 8 Both patterns were indexed using the program N-TREOR 24 implemented in Toby's CMPR toolkit, 25 revealing a doubling of the unit cell along c. Systematic absences were consistent with groups I2, Im, and I2/m. This doubling of the unit cell is not an effect of the presence of organic or fluoride guests because the calcined materials also show the extra reflections, always with a weak intensity.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

See 1 more Smart Citation

Zeolite Synthesis in Fluoride Media: Structure Direction toward ITW by Small Methylimidazolium Cations

et al. 2012

Self Cite

View full text Add to dashboard Cite

Pure silica ITW zeolite can be synthesized using 1,2,3-trimethylimidazolium and 1,3-dimethylimidazolium cations and fluoride anions as structure-directing agents (SDAs). Similarly to the previously reported 1,3,4-trimethylimidazolium, the dimethyl cation can also produce the zeolite TON, but this higher framework density phase finally transforms in situ into ITW. The structures of the as-made and calcined phases prepared with the new cations show a unit cell doubling along z, and the refined structures are reported. Periodic Density Functional Theory calculations provide the energies of the six SDA-ITW and SDA-TON zeolites, and their relative stabilities fully agree with the experimental observations. Structure-direction in this system is discussed from experimental and theoretical results that give strong support to the idea that strained silica frameworks are made possible in fluoride media by decreasing the covalent character of the Si-O bond. This decreased covalency is enhanced with the 1,2,3-trimethyl isomer, which is shown to be the strongest SDA for ITW and, at the same time, is the more hydrophilic of the three SDAs tested. Our observations with the three SDAs agree with the so-called Villaescusa's rule, i.e., the low framework density phase is favored at higher concentrations, but at the same time question the supersaturation hypothesis that has been proposed to explain this rule, since here the low-density phase is the most stable one.

show abstract

Section: ■ Experimental Sectionsupporting

confidence: 71%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Zeolite Synthesis in Fluoride Media: Structure Direction toward ITW by Small Methylimidazolium Cations

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…For as-synthesized zeolite ITW, the relatively large N,N 0 ,2-trimethylimidazolium SDA + molecules are expected to reside within the large [4 4 5 4 6 4 8 4 ] cages of the ITW framework formed by six interconnected D4R cages. 36 Similarly for as-synthesized zeolite MTT, the larger N,N 0 -diisopropylimidazolium SDA + molecules are presumed to be within the 10-ring channels of the MTT framework. 22 However, for both as-synthesized ITW and MTT materials, the absence of indexable Journal of the American Chemical Society ARTICLE XRD reflections corresponding to the SDA + molecules indicates that the organocations do not exhibit high degrees of long-range atomic order with respect to their distributions and/or configurations within their respective cages or channels.…”

Section: ' Results and Discussionmentioning

confidence: 99%

“…Yang et al 36 previously proposed a lower symmetry space group to account for the greater number of distinct 29 Si sites observed in 29 Si MAS NMR spectra of calcined zeolite ITW. On the basis of Rietveld refinement analyses of synchrotron X-ray diffraction data and energy minimization calculations, they suggested the Cm space group for the structure of as-synthesized zeolite ITW.…”

Section: ' Results and Discussionmentioning

confidence: 99%

Structure-Directing Roles and Interactions of Fluoride and Organocations with Siliceous Zeolite Frameworks

Shayib

George²,

Seshadri³

et al. 2011

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Interactions of fluoride anions and organocations with crystalline silicate frameworks are shown to depend subtly on the architectures of the organic species, which significantly influence the crystalline structures that result. One- and two-dimensional (2D) (1)H, (19)F, and (29)Si nuclear magnetic resonance (NMR) spectroscopy measurements establish distinct intermolecular interactions among F(-) anions, imidazolium structure-directing agents (SDA(+)), and crystalline silicate frameworks for as-synthesized siliceous zeolites ITW and MTT. Different types and positions of hydrophobic alkyl ligands on the imidazolium SDA(+) species under otherwise identical zeolite synthesis compositions and conditions lead to significantly different interactions between the F(-) and SDA(+) ions and the respective silicate frameworks. For as-synthesized zeolite ITW, F(-) anions are established to reside in the double-four-ring (D4R) cages and interact strongly and selectively with D4R silicate framework sites, as manifested by their strong (19)F-(29)Si dipolar couplings. By comparison, for as-synthesized zeolite MTT, F(-) anions reside within the 10-ring channels and interact relatively weakly with the silicate framework as ion pairs with the SDA(+) ions. Such differences manifest the importance of interactions between the imidazolium and F(-) ions, which account for their structure-directing influences on the topologies of the resulting silicate frameworks. Furthermore, 2D (29)Si{(29)Si} double-quantum NMR measurements establish (29)Si-O-(29)Si site connectivities within the as-synthesized zeolites ITW and MTT that, in conjunction with synchrotron X-ray diffraction analyses, establish insights on complicated order and disorder within their framework structures.

show abstract

“…This allows the smaller T -O -T bond angles in the D4R units that otherwise would incur an energetic penalty to the structure. All-silica syntheses with fluoride have yielded the novel zeolites ITQ-7 [53], ITQ-12 [54,55], and ITQ-13 [56]; each of these zeolites possesses D4R units.…”

Section: Synthesis In Fluoride Mediamentioning

confidence: 99%

The chemistry of phase selectivity in the synthesis of high-silica zeolites

Burton

Zones

Elomari

2005

Current Opinion in Colloid & Interface Science

122

109

View full text Add to dashboard Cite

Synthesis and Crystal Structure of As-Synthesized and Calcined Pure Silica Zeolite ITQ-12

Cited by 64 publications

References 22 publications

Zeolite Synthesis in Fluoride Media: Structure Direction toward ITW by Small Methylimidazolium Cations

Zeolite Synthesis in Fluoride Media: Structure Direction toward ITW by Small Methylimidazolium Cations

Structure-Directing Roles and Interactions of Fluoride and Organocations with Siliceous Zeolite Frameworks

The chemistry of phase selectivity in the synthesis of high-silica zeolites

Contact Info

Product

Resources

About