Unveiling the impact of second-order 1H-17O Quadrupolar-Dipolar interaction on solid-state NMR spectroscopy

• Theoretical insights were provided on the influence of second-order quadrupolar-dipolar (2nd-QD) cross interaction on solid-state NMR spectroscopy. • An efficient simulation strategy was introduced to account for 2nd-QD interaction between a spin-1/2 and half-integer quadrupolar nuclear spin pair. • The influence of 1 H- 17 O 2nd-QD interaction was demonstrated on 17 O-enriched dehydrated zeolites, MOR (8-MR and 12-MR channel structure) and FER (8-MR and 10-MR channel structure). Recent advances in the 17 O-enrichment techiques and high-resolution nuclear magnetic resonance (NMR) methods have opened new opportunities to utilize 17 O NMR to disentangle the zeolitic structure−property relationship that has not been well resolved through traditional 1 H, 27 Al, and 29 Si NMR spectroscopy. Compared with one-dimensional 17 O magic angle spinning (MAS) NMR experiments, 1 H- 17 O correlation spectrocopy has become a crucial method for revealing the structures and dynamics of reactive hydroxyl species in zeolites with higher resolution and precision. However, the introduction of 17 O can induce changes in 1 H MAS NMR signals due to the second-order 1 H- 17 O quadrupolar-dipolar (2nd-QD) cross interaction, which has recently been revealed by us on H-ZSM-5 (H-MFI) zeolites with 10-membered-ring (MR) channels. Herein, we performed various 1 H- 17 O correlation experiments ( 1 H{ 17 O}- J -heteronuclear multiple quantum coherence (HMQC), 1 H{ 17 O}- D -HMQC, and 1 H→ 17 O- D -RINEPT) on two other types of 17 O-enriched zeolites, i.e., H-Mordenite (H-MOR) with 8-/12-MR channels and H-ZSM-35 (H-FER) with 8-/10-MR channels. Notably, unusual 1 H- 17 O correlation signals with tilted patterns and magnetic-field-dependent shifts were observed on both samples and all tested correlation experiments at high fields up to 18.8 T. These observations were further comprehensively explained by theoretical analysis of the 1 H- 17 O quadrupolar-dipolar interaction, thus demonstrating that the 1 H- 17 O 2nd-QD interaction generally affects the 1 H and 1 H- 17 O correlation MAS NMR spectra of the dehydrated 17 O-enriched zeolites, irrespective of the framework types. Beyond zeolites, the non-ignorable 2nd-QD interaction on NMR spectroscopy can complicate NMR identification of 17 O-labeled hydroxyls in many other inorganic materials and biomolecules. The analysis methods proposed in this study are expected to effectively address these challenges and provide clearer insights into such systems.