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Ionothermal O-17 enrichment of oxides using microlitre quantities of labelled water

Research output: Contribution to journalJournal article

Published
  • John M. Griffin
  • Lucy Clark
  • Valerie R. Seymour
  • David W. Aldous
  • Daniel M. Dawson
  • Dinu Iuga
  • Russell E. Morris
  • Sharon E. Ashbrook
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<mark>Journal publication date</mark>2012
<mark>Journal</mark>Chemical Science
Issue number7
Volume3
Number of pages8
Pages (from-to)2293-2300
<mark>State</mark>Published
<mark>Original language</mark>English

Abstract

We present an ionothermal-based method for the simple and low-cost enrichment in O-17 of oxide materials. This is demonstrated for the case of SIZ-4, an ionothermally-prepared aluminophosphate framework with the CHA topology. A preliminary study of unenriched samples of SIZ-4 highlights the importance of the careful choice of template in order to obtain an ordered structure. We then show how an ionothermal synthesis procedure incorporating microlitre quantities of O-17-enriched H2O enables as-prepared and calcined samples of SIZ-4 to be obtained with O-17 enrichment levels that are sufficient to enable the recording of high-quality O-17 solid-state NMR spectra. While second-order quadrupolar-broadened resonances are unresolved in O-17 MAS NMR spectra, O-17 double-rotation (DOR) and multiple-quantum (MQ) MAS NMR spectra reveal distinct resonances that are partially assigned by comparison with NMR parameters derived using first-principles calculations. The calculations also enable an investigation of the dependence of O-17 NMR parameters on the local structural environment. We find that both the O-17 isotropic chemical shift and quadrupolar coupling constant show clear dependencies on Al-O-P bond lengths, and angles and will therefore provide a sensitive probe of structure and geometry in aluminophosphate frameworks in future studies.