Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Ionothermal O-17 enrichment of oxides using microlitre quantities of labelled water
AU - Griffin, John M.
AU - Clark, Lucy
AU - Seymour, Valerie R.
AU - Aldous, David W.
AU - Dawson, Daniel M.
AU - Iuga, Dinu
AU - Morris, Russell E.
AU - Ashbrook, Sharon E.
PY - 2012
Y1 - 2012
N2 - 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.
AB - 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.
KW - SOLID-STATE O-17
KW - STRUCTURE DIRECTING AGENT
KW - QUANTUM MAS NMR
KW - 1ST-PRINCIPLES CALCULATIONS
KW - QUADRUPOLAR NUCLEI
KW - DOUBLE-ROTATION
KW - IONIC LIQUIDS
KW - RESOLUTION
KW - ZEOLITE
KW - PARAMETERS
U2 - 10.1039/c2sc20155k
DO - 10.1039/c2sc20155k
M3 - Journal article
VL - 3
SP - 2293
EP - 2300
JO - Chemical Science
JF - Chemical Science
SN - 2041-6520
IS - 7
ER -