Atomic locations and adsorbate interactions of Al single and pair sites in H-ZSM-5 zeolite

• 成果类型: Article
• 署名作者: Li, Guangchao; Foo, Christopher; Fan, Raymond; Zheng, Mingji; Wang, Qiang; Chu, Yueying; Li, Jiasi; Day, Sarah; Steadman, Paul; Tang, Chiu; Lo, Tsz Woon Benedict; Deng, Feng; Tsang, Shik Chi Edman
• 署名单位: University of Oxford; Hong Kong Polytechnic University; Diamond Light Source; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC); STFC Rutherford Appleton Laboratory; Chinese Academy of Sciences; Innovation Academy for Precision Measurement Science & Technology, CAS; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-8913
• DOI: 10.1126/science.adq6644
• 发表日期: 2025-01-24
• 页码: 388-393
• 关键词: nmr-spectroscopy; acid sites; FRAMEWORK; aluminum; zsm-5; ammonia; mas; adsorption; nanosheets; occupancy

摘要

The distribution of substitutional aluminum (Al) atoms in zeolites affects molecular adsorbate geometry, catalytic activity, and shape and size selectivity. Accurately determining Al positions has been challenging. We used synchrotron resonant soft x-ray diffraction (RSXRD) at multiple energies near the Al K-edge combined with molecular adsorption techniques to precisely locate single Al and Al pairs in a commercial H-ZSM-5 zeolite. This analysis depicts three distinct Al tetrahedral (T) sites: T8, T6, and T4. A combined suite of characterizations, including ammonia temperature-dependent desorption, neutron powder diffraction, solid-state nuclear magnetic resonance spectroscopy, and density functional theory calculations, reveal isolated ammonia adsorption on T8 as single Al in the straight channel and bridged ammonia adsorption on T6 and T4 as an Al pair (Al-T6-O-Si-T5-O-Al-T4) in the straight-sinusoidal intersection.