Related Experiment Video
Updated: May 11, 2026
08:26
Synthesis of Zeolites Using the ADOR Assembly-Disassembly-Organization-Reassembly Route
Published on: April 3, 2016
13.2K
Refining siliceous zeolite framework structures with 29Si 2D J-resolved NMR spectroscopy
Deepansh J Srivastava1, Maxwell C Venetos2, Lexi McCarthy-Carney3
1Hyperfine, Inc., Guilford, CT, USA. dsrivastava@hyperfine.io.
Physical Chemistry Chemical Physics : PCCP
|December 9, 2024
Summary
A new 2D J-resolved spectroscopy method enhances crystalline silicate structure analysis. This technique refines zeolite structures by improving distance measurements and spectral coupling agreement.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Materials Science
- Crystallography
Background:
- Characterizing crystalline silicate structures is crucial for understanding their properties and applications.
- Traditional methods may have limitations in resolving detailed structural information, especially for complex frameworks.
Purpose of the Study:
- To develop a novel 2D J-resolved spectroscopy technique for natural abundance 29Si NMR.
- To apply this technique for refining the structures of crystalline silicates, specifically zeolites Sigma-2 and ZSM-12.
- To establish a strategy for structure refinement using NMR-derived distance restraints and spectral parameters.
Main Methods:
- Development of a modified shifted-echo PIETA pulse sequence for 29Si 2D J-resolved NMR.
- Acquisition of spectra for Sigma-2 and ZSM-12 zeolites.
- Utilizing Si-O, O-O, and Si-Si distances, along with 29Si chemical shifts and 2JSi-O-Si couplings for structure refinement.
Main Results:
- The 29Si 2D J-resolved spectra provided valuable structural insights.
- Refinement of the Sigma-2 structure showed excellent agreement in Si-O and O-O distances with single-crystal X-ray diffraction (SCXRD) data.
- Refinement of the ZSM-12 structure, initially determined by synchrotron powder XRD, demonstrated improved Si-O and O-O distances and better correlation between calculated and experimental NMR parameters.
Conclusions:
- The developed 2D J-resolved NMR method is effective for analyzing natural abundance 29Si in crystalline silicates.
- This NMR-based strategy offers a powerful complementary approach to X-ray diffraction for detailed structure determination and refinement.
- The technique provides enhanced accuracy in structural parameters and spectral correlations for zeolites.
Related Concept Videos
01:20NMR Spectrometers: Overview
NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:12Two-Dimensional (2D) NMR: Overview
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
01:14NMR Spectroscopy of Aromatic Compounds
Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...