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Dynamics on the microsecond timescale in microporous aluminophosphate AlPO-14 as evidenced by Al-27 MQMAS and STMAS NMR spectroscopy

Antonijevic, Sasa; Ashbrook, Sharon E; Walton, Richard; Wimperis, Stephen and Yang, Huaixin Yang (2006). Dynamics on the microsecond timescale in microporous aluminophosphate AlPO-14 as evidenced by Al-27 MQMAS and STMAS NMR spectroscopy. Journal of the American Chemical Society, 128(24) pp. 8054–8062.

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Multiple-quantum magic angle spinning (MQMAS) and satellite-transition magic angle spinning (STMAS) are two well-known techniques for obtaining high-resolution, or "isotropic", NMR spectra of quadrupolar nuclei. It has recently been shown that dynamics-driven modulation of the quadrupolar interaction on the microsecond timescale results in linewidths in isotropic STMAS spectra that are strongly broadened, while, in contrast, the isotropic MQMAS linewidths remain narrow. Here, we use this novel methodology in an (27)AI (I = 5/2) NMR study of the calcined-dehydrated aluminophosphate AIPO-14 and two forms of as-synthesized AlPO-14, one prepared with isopropylamine (C3H7NH2) as the template molecule and one with piperidine (C5H10NH). For completeness, the P-31 and C-13 (both I=1/2) MAS NMR spectra are also presented. A comparison of the (27)AI MQMAS and STMAS NMR results show that, although calcined AIOPO-14 appears to have a rigid framework structure, the extent of motion in the two as-synthesized forms is significant, with clear evidence for dynamics on the microsecond timescale in the immediate environments of all four AI sites in each material. Variable-temperature (27)AI STMAS NMR studies of the two as-synthesized AIPO forms reveal the dynamics to be complex, with the motions of both the guest water molecules and organic template molecules shown to be contributing. The sensitivity of the STMAS NMR experiment to the presence of microsecond timescale dynamics is such that it seems likely that this methodology will prove useful in NMR studies of host-guest interactions in a wide variety of framework materials.

Item Type: Journal Article
ISSN: 0002-7863
Keywords: solid-state NMR; angle-spinning NMR; experiments involving quadrupolar; as-synthesized alpo4-14; transition MAS NMR; multiple-quantum; molecular-sieves; nuclei; resolution; p-31
Academic Unit/Department: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Life, Health and Chemical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 6139
Depositing User: Astrid Peterkin
Date Deposited: 05 Jan 2007
Last Modified: 04 Oct 2016 09:57
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