Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

Abstract

In the past two decades, metal fluorides have gained importance in the field of heterogenous catalysis of bond activation reaction, e.g., hydrofluorination. One of the most investigated metal fluorides is AlF3. Together with its chlorine-doped analogon aluminiumchlorofluoride (AlClxF3−x, x = 0.05–0.3; abbreviated ACF), it has attracted much attention due to its application in catalysis. Various surface models for α-AlF3 and their chlorinated analogues (as representatives of amorphous ACF) are investigated with respect to their Lewis acidity of the active centres. First-principle density functional theory (DFT) methods with dispersion correction are used to determine the adsorption structure and energy of the probe molecules CO and NH3. The corresponding vibrational frequency shift agrees well with the measured values. With this insight we predict the local structure of the active sites and can clarify the importance of secondary interactions to the local anionic surrounding of the catalytic site.

CO adsorption on pure, defective and mixed composition AlF3 and MgF2 surfaces

“…Previous theoretical modelling 28 also explored CO binding to pristine α-AlF 3 and found similar values to us for the (011̄0) surface (2165 cm −1 ), and higher values of 2190–2205 cm −1 for the unreconstructed (112̄0). For the (112̄2) surface (not considered here), they obtained 2187 cm −1 on the tetrahedral site and 2158 cm −1 on the five-fold coordinated site.…”

MAO- and Borate-Free Activating Supports for Group 4 Metallocene and Post-Metallocene Catalysts of α-Olefin Polymerization and Oligomerization

“…It is relevant to remind here that crystalline AlF 3 was found to be a low-efficient activating support for Zr1 in the presence of Me 3 Al in the early work of Soga and Kaminaka [ 75 ]. It is quite possible that these unsuccessful experiments were conducted with large-sized crystallites of α-AlF 3 , whereas AlF 3 showed high Lewis acidity only as β-AlF 3 crystal modification or in the amorphous form [ 208 , 209 ]. Efficient methods of the synthesis of high-surface amorphous AlF 3 have been developed in the early 2000s [ 210 , 211 ].…”

Synthesis under Normal Conditions and Morphology and Composition of AlF3 Nanowires

“…Metal fluorides are promising for catalysis applications [1][2][3][4][5], and are often used in C-H and C-F bond activation reactions or hydroarylation reactions, as ionic conductors [6] and luminescent materials [7][8][9][10], applying sol-gel technology with trifluoroacetic acid as a source of fluorine. In addition, ref.…”