Probing Interlayer Bromide in Solvent Intercalation of Layered Yttrium Hydroxide via 79/81Br SSNMR Spectroscopy

Layered metal hydroxides can be exfoliated into functional nanosheets via solvent intercalation, yet probing the atomic-level solvation processes remains challenging. Herein, we employ 79/81 Br solid-state nuclear magnetic resonance (SSNMR) spectroscopy to directly probe the local environments of interlayer anions in bromide-intercalated layered yttrium hydroxide (LYH-Br). Upon treatment with a series of solvents of varying polarity, the overall spectral lineshapes remain largely unchanged in weakly interacting systems (toluene (PhMe), acetone (ACE), isopropanol (IPA)), indicating preservation of the local structural framework. Increasing solvent polarity leads to a reduction in 79 Br NMR signal intensity, particularly in the case of formamide (FM). By combining complementary characterization techniques and transverse relaxation analysis, we show that this signal attenuation originates from shortened T 2 relaxation times rather than structural degradation. These results reveal that polar solvent intercalation perturbs the local dynamics and solvation environment of interlayer Br − anions. Furthermore, solvent-induced effects are largely reversible for PhMe, ACE, IPA and N, N-dimethylformamide (DMF) upon vacuum drying, whereas FM remains trapped within the interlayer spaces, illustrating stronger host-guest interactions and altered local dynamics. This work demonstrates solid-state 79/81 Br NMR as a powerful tool for directly distinguishing solvation-driven intercalation mechanisms in layered materials.