1H NMR study of water molecules confined in nanochannels of mordenite

23Na and 27Al NMR Study of Structure and Dynamics in Mordenite

“…The same conclusion follows from the comparison of the 27 Al NMR spectra obtained at T  = 300 and 390 K measured with and without 1 H decoupling, which are shown in Fig. 2a, c. These spectra show the same lineshape and width, indicating that the dipolar interactions between of 27 Al and 1 H nuclei are very small in the range from 300 to 390 K. This finding is in agreement with the flipping and diffusion of water molecules along the mordenite channels obtained by 1 H NMR [5], which results in an effective averaging of the above-mentioned contribution at T  > 300 K.…”

“…The obtained activation energy of ~21 kJ/mol suggests that the modulation of quadrupole interactions by means of translational and reorientational jumps of electric dipoles of water molecules [4, 5] is responsible for the relaxation process of the 27 Al and 23 Na nuclei. From the data represented in Table 1, the averaged fluctuations of the quadrupole coupling constants are found to be for 27 Al nuclei and for 23 Na nuclei.…”

“…The dynamics of water molecules in mordenite have been studied by nuclear magnetic resonance (NMR) [4, 5]. Analysis of the temperature dependencies of the proton spin-relaxation times in the laboratory and rotating frames ( T 1 and T 1ρ ) revealed diffusion of water molecules along the channels above T  = 200 K. Temperature dependencies of the 1 H dipolar spin-relaxation time T 1D showed that the dipolar relaxation in mordenite is responsive to slow 180° reorientations (flips) of water molecules around their second-order symmetry axes.…”

Proton Dipolar Spin–Lattice Relaxation in Nano-channels of Natrolite

“…Contribution to T 1D −1 , coming from the interaction of 1 H nuclear spins and unpaired electron spins of paramagnetic defects/impurities, may be described by the expression [ 32 – 34 ] where A 1e is the amplitude of the fluctuating local magnetic fields induced by the electron–nuclear interaction, and τ ce is the correlation time of this process. Therefore, the experimental dependence of the dipolar relaxation rate, R 1D, in the natrolite may be described by the expression …”