Specific lift-up behaviour of acetate-intercalated layered yttrium hydroxide interlayer in water: application for heterogeneous Brønsted base catalysts toward Knoevenagel reactions

Hara, Takayoshi; Habe, Maoko; Nakanishi, Hiroyuki; Fujimura, Takuya; Sasai, Ryo; Moriyoshi, Chikako; Kawaguchi, Shogo; Ichikuni, Nobuyuki; Shimazu, Shogo

doi:10.1039/d1cy02328d

Cited by 4 publications

(1 citation statement)

References 65 publications

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“…LYH-Br belongs to a new family of anion-exchangeable layered metal hydroxides, exhibiting various potential applications in catalysis, − adsorption, , luminescence, − etc. − LYH-Br was proposed to adopt the crystal structure of LYbH-Cl (Yb 4 (OH) 10 Cl 2 ·3H 2 O), and its unit cell parameters and atomic coordinates were obtained by a combination of 1D and 2D 89 Y solid-state NMR, PXRD, and DFT methods . As Figure illustrates, LYH-Br consists of positively charged yttrium hydroxide layers and intercalated charge-balancing anions.…”

Section: Resultsmentioning

confidence: 99%

Mapping Hydrogens in Hydrous Materials

et al. 2023

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Hydrous materials such as clays, cements, hydroxyapatite, and metal hydroxides have been known and extensively used since antiquity. However, experimental elucidation of hydrogen in hydrous materials remains challenging due to the intrinsic insensitivity, limited accessibility, sample damage, or poor spectral resolution of many characterization methods. 1 H solid-state NMR spectroscopy has evolved into an ideal site-specific characterization tool of hydrogen-containing materials, but its current application in hydrous materials is hampered by the low resolution of 1 H NMR spectra in the solid state due to the presence of intense dipolar coupling networks and a narrow 1 H chemical shift range. Herein, a significant advance in the characterization of hydrogens in hydrous materials is reported. A combination of magic-angle spinning (MAS) NMR, moderate 2 H substitution, and high magnetic fields has unlocked the capacity of identifying many chemically similar while crystallographically distinct hydrogen sites in a prototypical hydrous material Y 4 (OH) 10 Br 2 •3H 2 O (LYH-Br) by 1D 1 H solid-state NMR experiments. 1 H NMR peaks were first tentatively assigned in accordance with the density functional theory (DFT) calculation results, and the assignment was further refined by 2D 1 H− 89 Y heteronuclear correlation (HETCOR) and 1 H− 1 H doublequantum (DQ) MAS NMR data. The order of 1 H chemical shift (δ iso ) values provides valuable information on the relative strength of hydrogen bond for ten hydroxide hydrogen sites. The power of very high spectral resolution is further described by observing all triple-quantum (TQ) coherences in the 2D 1 H− 1 H TQ MAS NMR spectrum, in which all spatial proximities among three hydrogen sites are resolved. This demonstration of the very high spectral resolution obtained in 1D and 2D 1 H solid-state NMR experiments illustrates how scientists in various communities can now study the multiple hydrous species of hydrous materials and obtain previously inaccessible fine structural information.

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