- journal_title：American Mineralogist
- Contributor：Brian L. Phillips ; Harris E. Mason ; Stephen Guggenheim
- Publisher：Mineralogical Society of America
- Date：2007-
- Format：text/html
- Language：en
- Identifier：10.2138/am.2007.2417
- journal_abbrev：American Mineralogist
- issn：0003-004X
- volume：92
- issue：8-9
- firstpage：1474
- section：Articles
Using 29Si, 1H, and 2H magic-angle spinning (MAS) and 29Si{1H} heteronuclear correlation (Het-Cor) nuclear magnetic resonance (NMR) spectroscopy the tetrahedral sheets of the 10 Å phase are shown to contain Q2-type Si bonded to silanol groups that donate hydrogen bonds to interlayer H2O. 29Si NMR spectra of 10 Å phase samples synthesized from oxide and from crystalline talc starting materials contain a peak near −87 ppm for Q2 Si, in addition to the main peak at −98 ppm for the talc-like Q3 of the tetrahedral sheet. The 1H MAS NMR spectra of the 10 Å phase contain two distinct peaks, at chemical shifts of +7.8 and +3.2 ppm, in addition to a narrow peak near +0.9 ppm from the talc-like hydroxyl groups. 29Si{1H} HetCor data indicate that the +7.8 ppm 1H resonance corresponds to silanol groups and that at +3.2 ppm arises from interlayer H2O. Comparison of the observed data with correlations of 1H NMR chemical shift and 2H quadrupolar coupling indicates that the silanol groups donate moderate hydrogen bonds to interlayer H2O, d(O···O) ≈ 2.8 Å, whereas most interlayer H2O donate only very weak or no hydrogen bonds at ambient conditions. Our results suggest that formation of the 10 Å phase involves formation of vacancies, which allow favorable hydrogen bond interaction between interlayer H2O and the normally hydrophobic talc-like 2:1 layers.