Computational Study of Brønsted Acidity of Faujasite. Effect of the Al Content on the Infrared OH Stretching Frequencies SastreGerman KatadaNaonobu SuzukiKatsuki NiwaMiki 2008 In this study we use the experimental data from a commercial sample of faujasite (Si/Al ∼ 2.5) and we compare the infrared OH stretching bands with periodic density functional calculations of a faujasite unit cell of composition Si<sub>34</sub>Al<sub>14</sub>O<sub>96</sub>H<sub>14</sub> (Si/Al = 2.4). Assuming that O4H is not populated, the computational results show the following bands for O1H, O2H, and O3H: 3588−3689, 3555−3588, and 3517−3560 cm<sup>−1</sup>, respectively, which are in good agreement with the experimental values of 3648, 3571, and 3526 cm<sup>−1</sup>, respectively. We have studied how the OxH frequencies (<i>x</i> = 1−4) change due to the presence of two neighbor Al centers (Si<sub>46</sub>Al<sub>2</sub>O<sub>96</sub>H<sub>2</sub>, Si/Al = 23), with respect to the isolated case (Si<sub>47</sub>Al<sub>1</sub>O<sub>96</sub>H<sub>1</sub>, Si/Al = 47). The experimental infrared bands cannot be explained by the high silica models (Si/Al = 47, 23) and can only be explained when taking into account (i) the experimental Al content, by using a Si<sub>34</sub>Al<sub>14</sub>O<sub>96</sub>H<sub>14</sub> model, (ii) the experimental OH population, and (iii) the experimental Si(<i>n</i>Al) (<i>n</i> = 0−4) population.