Eilertsen, Einar A. and Ogino, Isao and Hwang, Son-Jong and Rea, Thomas and Yehb, Sheila and Zones, Stacey I. and Katz, Alexander (2011) Nonaqueous Fluoride/Chloride Anion-Promoted Delamination of Layered Zeolite Precursors: Synthesis and Characterization of UCB-2. Chemistry of Materials, 23 (24). pp. 5404-5408. ISSN 0897-4756 http://resolver.caltech.edu/CaltechAUTHORS:20120124-093410331
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The delamination of layered zeolite precursor PREFER is demonstrated under mild nonaqueous conditions using a mixture of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride in N,N-dimethylformamide (DMF) as solvent. The delamination proceeds through a swollen material intermediate which is characterized using powder X-ray diffraction (PXRD). Subsequent addition of concentrated HCl at room temperature leads to synthesis of UCB-2 via delamination of the swollen PREFER material and is characterized using PXRD, transmission electron microscopy (TEM), and argon gas physisorption, which shows lack of microporosity in UCB-2. ^(29)Si magic angle spinning (MAS) NMR spectroscopy indicates lack of amorphization during delamination, as indicated by the entire absence of Q^2 resonances, and ^(27)Al MAS NMR spectroscopy shows exclusively tetrahedral aluminum in the framework following delamination. The delamination process requires both chloride and fluoride anions and is sensitive to solvent, working well in DMF. Experiments aimed at synthesizing UCB-2 using aqueous conditions previously used for UCB-1 synthesis leads to partial swelling and lack of delamination upon acidification. A similar lack of delamination is observed upon attempting synthesis of UCB-1 under conditions used for UCB-2 synthesis. The delamination of PREFER is reversible between delaminated and swollen states in the following manner. Treatment of as-made UCB-2 with the same reagents as used here for the swelling of PREFER causes the delaminated UCB-2 material to revert back to swollen PREFER. This causes the delaminated UCB-2 material to revert back to swollen PREFER. Altogether, these results highlight delamination as the reverse of zeolite synthesis and demonstrate the crucial role of noncovalent self-assembly involving the zeolitic framework and cations/anions/structure-directing agent and solvent during the delamination process.
|Additional Information:||© 2011 American Chemical Society. Received: August 18, 2011. Revised: September 19, 2011. Publication Date (Web): November 23, 2011. E.A.E. is grateful to to the Norwegian Research Council KOSKII for a fellowship at the University of California, Berkeley. The authors acknowledge Prof. Enrique Iglesia for helpful discussion and Dr. Alexander Kuperman for the idea to relate layered zeolite precursor delamination to zeolite synthesis. The authors are grateful to the Management and Transfer of Hydrogen via Catalysis Program funded by Chevron Corporation for financial support. The NMR facility at Caltech was supported by the National Science Foundation (NSF) under Grant Number 9724240 and partially supported by the MRSEC Program of the NSF under Award Number DMR-520565.|
|Subject Keywords:||delamination; exfoliation; layered zeolite precursor; PREFER|
|Official Citation:||Nonaqueous Fluoride/Chloride Anion-Promoted Delamination of Layered Zeolite Precursors: Synthesis and Characterization of UCB-2 Einar A. Eilertsen, Isao Ogino, Son-Jong Hwang, Thomas Rea, Sheila Yeh, Stacey I. Zones, and Alexander Katz Chemistry of Materials 2011 23 (24), 5404-5408|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||24 Jan 2012 17:50|
|Last Modified:||27 Dec 2012 08:05|
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