Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, CZ-128 40, Prague 2, Czech Republic.
Phys Chem Chem Phys. 2010 Feb 21;12(7):1497-506. doi: 10.1039/b917969k. Epub 2010 Jan 14.
Periodic DFT calculations were performed on H-FER models having Si/Al ratios of 71 : 1, 35 : 1 and 8 : 1, in order to investigate the effect of aluminium content on the properties of the zeolite Brønsted acid sites. Relative stability of these sites was found to be dependent on Si/Al ratio, which is the main factor dictating the relative concentration of Brønsted acid sites having different types of local configuration, to the point that some types of acid site are formed only when the aluminium content of the zeolite is relatively high. The number of AlO(4) tetrahedra sharing an oxygen with the SiO(4) tetrahedron involved in the Brønsted acid site determines the Si-O(H)-Al angle, O-H stretching frequency and deprotonation energy (and hence acid strength). For Brønsted acid protons not involved in intra-zeolite H-bonding, a correlation was found between Si-O(H)-Al angle and O-H stretching frequency.
为了研究铝含量对沸石 Brønsted 酸位性质的影响，对 Si/Al 比分别为 71:1、35:1 和 8:1 的 H-FER 模型进行了周期性 DFT 计算。这些酸位的相对稳定性取决于 Si/Al 比，这是决定具有不同局部构型的 Brønsted 酸位相对浓度的主要因素，以至于某些类型的酸位只有在沸石的铝含量相对较高时才会形成。参与 Brønsted 酸位的 AlO(4)四面体与 SiO(4)四面体共用氧的数目决定了 Si-O(H)-Al 角、O-H 伸缩频率和去质子化能（因此决定了酸强度）。对于不参与沸石内 H 键合的 Brønsted 酸质子，发现 Si-O(H)-Al 角与 O-H 伸缩频率之间存在相关性。
