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

High resolution 17 O NMR spectra of siliceous ferrierite (Sil-FER) have been collected and the 29 Si and 17 O isotropic chemical shifts and the electric field gradients of oxygen have been calculated from first principles. The theoretical 29 Si 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 17 O 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 17 O NMR parameters.