Combined Solid-State NMR and Theoretical Calculation Studies of Brønsted Acid Properties in Anhydrous 12-Molybdophosphoric Acid

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• 作者：Ningdong Feng ; Anmin Zheng ; Shing-Jong Huang ; Hailu Zhang ; Ningya Yu ; Chih-Yi Yang ; Shang-Bin Liu ; Feng Deng
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：September 16, 2010
• 年：2010
• 卷：114
• 期：36
• 页码：15464-15472
• 全文大小：454K
• 年卷期：v.114,no.36(September 16, 2010)
• ISSN：1932-7455

文摘

The strength and distribution of Brønsted acidic protons in anhydrous phosphomolybdic acid (H₃PMo₁₂O₄₀, HPMo) have been studied by solid-state magic-angle-spinning (MAS) NMR, using trimethylphosphine oxide (TMPO) as the probe molecule in conjunction with density functional theory (DFT) calculations. Brønsted acid sties with strengths exceeding the threshold of superacidity (Zheng, A. et al. J. Phys. Chem. B 2008, 112, 4496) were observed for HPMo. In addition, the locations and adsorption structures of Brønsted protons on various oxygen sites in HPMo were also identified. The preferred location of the acidic proton was found to follow the trend: corner-sharing (O_b) > edge-sharing (O_c) terminal (O_d) sites. Moreover, a tendency of hybridization among Brønsted protons residing at O_b and O_c sites of HPMo was inferred by experimental as well as theoretical ³¹P chemical shifts of the adsorbed TMPO.