关键词: 固体酸, 分子筛, 固体核磁共振, 酸性位, 溶剂化诱导效应, 量子化学计算, ONIOM方法

Abstract: In this dissertation, quantum chemical calculations and NMR experimental methods were combined to study in detail the acidities of zeolite H-MCM-22 and commercialized catalyst BF₃/γ-Al₂O₃. In addition, a new computational scheme ONIOM-GIAO was applied to calculate the NMR parameters of large systems. 
(1) We applied the new embedding NMR calculational method ONIOM-GIAO to accurately predict ¹³C NMR chemical shifts of amino acids as well as a series of organic species absorbed on zeolites. Since the effects of framework nvironments around the part interested or active center have been taken into account by the ONIOM method, the ¹³C chemical shifts predicted by the ONIOM-GIAO are in well agreement with the NMR experimental values.
(2) The distribution of Brǒnsted acidic protons and their acid strengths in zeolite H-MCM-22 have been characterized by density functional theory (DFT) calculations as well as probe molecule magic angle spinning (MAS) NMR experiments. Our theoretical and experimental results may partially explain the special selectivity of acid-catalyzed reactions occurring inside the channels of H-MCM-22 zeolite.
(3) Based on the multinuclear solid-state NMR results, DFT calculations have revealed the detailed structures of various acid sites formed on the BF₃/γ-Al₂O₃ catalyst. The detailed mechanism of interaction between the BF₃ and γAl₂O₃ surface as well as the newly formed Brǒnsted and Lewis acid structures were proposed. The DFT computational results are well consistent with the NMR observations.
(4) Our theoretical calculations have revealed a new solvent-assisted proton transfer effect in zeolite catalysis. We found that when isopropanol was coadsorbed with the naphthalene molecule in the channels of zeolite mordenite, acid strength of the Brǒnsted acidic proton of the zeolite has been considerably increased, leading to the protonation of adsorbed isopropanol molecule. The big conjugate system of naphthalene molecule is likely to stabilize the resultant isopropanol carbenium cations by dispersing the charges around them.

Key words: Solid acids, Zeolites, Solid state NMR, Acid sties, Solvent -induced effect, Quantum chemical calculation, ONIOM