A High-Resolution ¹⁷O and ²⁹Si NMR Study of Zeolite Siliceous Ferrierite and ab Initio Calculations of NMR Parameters

Abstract

High resolution 17O NMR spectra of siliceous ferrierite (Sil-FER) have been collected and the 29Si and 17O isotropic chemical shifts and the electric field gradients of oxygen have been calculated from first principles. The theoretical 29Si MAS NMR spectrum is found to be in excellent quantitative agreement with the experimentally determined spectrum, and is extremely sensitive to the accuracy of the structure used for the calculations, thus providing a method for assessing the quality of the structure determination. However, theoretical predictions of the chemical shifts, quadrupolar coupling constants and asymmetry parameters show only qualitative agreement with the experimental 17O NMR spectra obtained by Double Rotation (DOR) and multiple quantum magic angle spinning (MQMAS) as the spectra are much more complex (10 peaks within a shift range of less than 15 ppm, and the quadrupolar coupling constants only differ by 0.4 MHz) and hence higher accuracy is required from the shift calculations (>0.5 ppm), which is currently not possible. These findings also demonstrate the current limitations of the experimental techniques and show that no simple correlation appears to exist between the zeolite structure, such as the Si−O−Si bond angles or lengths, and the 17O NMR parameters.

Ultra-high resolution 17O solid-state NMR spectroscopy of biomolecules: A comprehensive spectral analysis of monosodium L-glutamate·monohydrate

“…[15][16][17][18][19][20][21] It is worth noting that high-resolution 17 O NMR MQMAS and DOR have also been reported for many important inorganic materials. 5,[22][23][24] In comparison to inorganic materials, there are three major complications for 17 O solid-state NMR on bio/organic molecules: (1) the abundance of hydrogen in bio/organic molecules gives rise to significant dipolar broadening unless high power 1 H-decoupling is applied; (2) the quadrupole interaction is generally larger (7- 33 was used. The interaction between the valence electrons, and the nuclei and core electrons was described using ultrasoft pseudopotentials.…”

Calculated magnetic properties for the characterization of zeolite active sites

“…MAS NMR has been successfully applied to zeolites containing 7 Li, 11 B, 17 O, 23 Na, 29 Si, 27 Al and 31 P. 29 Si spectra have been particularly useful thanks to the wide range of 29 Si chemical shifts, very sensitive to the local geometry and electronic structure of the nearest neighbours. 3 -5 29 Si signals produced by crystallographically non-equivalent silicons can be obtained, as demonstrated in pioneering works on a highly siliceous silicalite 6,7 showing up to 20 well-resolved lines for the 24 sites.…”

“…In the first part of this contribution, we report the general effects of Al and B substitution in a zeolite framework, coupled with H C or Na C counter-ions, on the 29 Si, 27 Al and 11 B NMR spectra. Our results show how theoretical results can allow one to assign the experimental spectrum to two crystallographically distinct sites (i) when occupied by Si, (ii) when one Si is substituted by Al, (iii) when one Si is substituted by B and (iv) in both cases (Al and B), when the counter-ion changes from proton to sodium.…”

“…9.4 ppm. 60 From experimental and theoretical studies, it appears that NMR can be considered as a local property in zeolitic systems, since the values of 29 Si or 27 Al NMR chemical shifts are determined by the composition in Si and/or Al of the second shell of neighbours. 61 -65 The clusters used for the evaluation of the Si and Al NMR parameters contain thus the next O (first shell) and Si (second shell) neighbours and include a four-membered ring, found in the mazzite structure (Fig.…”

Solid-State17O NMR as a Probe for Structural Studies of Proteins in Biomembranes

“…Despite these difficulties, in recent years, with the advent of higher magnetic fields and techniques for improving resolution beyond magic angle spinning experiments (MAS), there has been a significant increase in 17 O NMR reports from inorganic materials, such as glasses and zeolites. 8,9 There has been much less 17 O NMR reported from organic materials since 17 O presents even more of a challenge due to the larger quadrupole interaction and, hence, larger line widths. 19 Recent reports of 17 O NMR from biologically relevant materials have included inorganic molecules interacting with hemeproteins, 10 polypeptides, 11,12 amino acids, 2 and nucleic acid bases.…”