2025-06-30 中国科学院 (CAS)
2D 1H−1H DQ-SQ NMR spectra of water adsorbed on USY zeolites with various water loadings: 0 (a), 15 (b), 30 (c), and 45 water/u.c. (d), slices extracted at δDQ = 6.5 and 7.3 ppm from 2D plots (e) and schematic of B/L synergistic sites formation by water hydrolysis on LAS (Al-OH) (f). (Image by APM)
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/chem/202507/t20250701_1046534.shtml
- https://pubs.acs.org/doi/10.1021/jacs.5c01756
固相NMR分光法によるゼオライト中のNMR-Invisible Alによる水誘起相乗酸性サイトの観測 Observation of Water-Induced Synergistic Acidic Site from NMR-Invisible Al in Zeolite via Solid-State NMR Spectroscopy
Xingxing Wang,Qiang Wang,Chao Wang,Yueying Chu,Min Hu,Feng Deng,Jihong Yu,and Jun Xu
Journal of the American Chemical Society Published: May 19, 2025
DOI:https://doi.org/10.1021/jacs.5c01756
Abstract
Zeolites are highly sensitive to water, which significantly affects their acidity─a key factor in catalytic reactions. This study investigates the dynamic interactions between water and often overlooked active sites, specifically the “NMR-invisible” aluminum species (tricoordinated framework Al─FAL and cationic extra-framework Al─EFAL) in ultrastable Y (USY) zeolite under ambient conditions. Using solid-state NMR spectroscopy combined with theoretical calculations, we demonstrate that water readily undergoes dissociative adsorption on these “NMR-invisible” Al sites. This process transforms both FAL and EFAL into “NMR-visible” Al species. The formation of new Brønsted acid sites on tetra-, penta-, and hexa-coordinated FAL results in an increase of over 60% in the BAS concentration in the USY zeolite. The hydrolysis of EFAL cations leads to the formation of Brønsted/Lewis acid synergistic sites, significantly improving the catalytic activity of USY zeolite. This enhancement is evident in the improved conversion of diethyl ether to ethene in the presence of moisture.
