Probing Local Structure of Layered Double Hydroxides with ¹H Solid-State NMR Spectroscopy on Deuterated Samples

Abstract

By using a simple and efficient deuteration process, (2)H has been successfully introduced into layered double hydroxides (LDHs). Due to significantly less (1)H-(1)H homonuclear dipolar coupling, high-resolution (1)H solid-state NMR spectra can now be obtained conveniently at medium to low spinning speed to extract the information of cation ordering in LDHs. Furthermore, we show that double-resonance experiments can be applied easily to investigate internuclear proximities and test possible cation-ordered superstructure models. This approach can be readily extended to LDHs with different compositions to explore the local structure and the key interactions between the cations in the layer and interlayer anions.

Identification of intrinsic hydrogen impurities in ZnO with 1H solid-state nuclear magnetic resonance spectroscopy

“…The broad resonance at 4.9 ppm can then be tentatively assigned to hydroxyl groups in -Zn(OH) 2 . The large linewidth of the peak is associated with large 1 H-1 H homonuclear dipolar coupling in -Zn(OH) 2 , which is often observed in the spectra of metal hydroxides [40,41] and consistent with the presence of large spinning sideband manifolds (-Zn(OH) 2 in Figure 1c). Deuteration has often been used to dilute 1 H and increase the spectra resolution [41].…”

“…The large linewidth of the peak is associated with large 1 H-1 H homonuclear dipolar coupling in -Zn(OH) 2 , which is often observed in the spectra of metal hydroxides [40,41] and consistent with the presence of large spinning sideband manifolds (-Zn(OH) 2 in Figure 1c). Deuteration has often been used to dilute 1 H and increase the spectra resolution [41]. The FT-IR data of deuterated -Zn(OH) 2 ( Figure S4) as well as NMR spin counting results suggest D has been successfully introduced to Zn(OH) 2 (see additional discussion in the supporting information).…”

Local environment and composition of magnesium gallium layered double hydroxides determined from solid-state 1H and 71Ga NMR spectroscopy

“…There is evidence of M(III)-rich regions with Al-O-Al connectivities in MgAl LDH's, which has been reported from 1 H and 27 Al SSNMR, [7,8] but not observed by Sideris et al [6,[9][10][11]. It is of interest to see if similar Ga rich regions can be found in the MgGa LDH.…”

“…Thus, the ordering of M(III) and M(II)/M(III) ratios can be determined if the -OH groups can be quantified. It has been demonstrated that solid-state NMR (SSNMR) provides this information and gave a detailed insight into local environment of the cation in magnesium aluminum (MgAl) LDH's [6][7][8][9][10][11], including the distribution of Al in the cation layer, the presence of structural defects -information which is very difficult determined with X-ray diffraction techniques, which rely on long range order. The dynamics and orientation of both inorganic and organic anions in the interlayer has been extensively studied by Kirkpatrick et al [12][13][14][15][16][17][18].…”

“…SSNMR studies have found MgAl LDH's to be ordered, but they may contain structural defects on the atomic level [7][8][9][10][11]. There are contradicting observations as to whether the structure contains Al-O-Al connectivities or not, which has been ascribed to different methods of [7].…”