Synthesis of Ti(OH)OF ⋅ 0.66 H<sub>2</sub>O in Imidazolium‐based Ionic Liquids

Sieland, Melanie; Camus-Génot, Valentine; Djerdj, Igor; Smarsly, Bernd M.

doi:10.1002/open.202000256

Cited by 1 publication

(9 citation statements)

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“…Otherwise, after the addition of H 2 O to the solution an immediate and heavy reaction of TiCl 4 would occur, resulting in the formation of other titanium oxides (e.g., anatase) instead of the uncommon HTB compound. 21 Hence, we prepared a sample containing 3.85 mmol C 4 mim BF 4 and 1.82 mmol TiCl 4 (standard ratio for a reaction leading to Ti(OH)OF•0.66H 2 O) 12 and measured different NMR spectra of this sample. The structure of the cation is not affected by the presence of TiCl 4 , since the 1 H and 13 C NMR spectra (see Figure S6) are comparable to the spectra of pure C 4 mim BF 4 .…”

Section: ■ Results and Discussionmentioning

confidence: 87%

“…Since evidently BF 4 − has to be hydrolyzed during the reaction, the IL anion acts as a reactant. 11,12 Prior to interpreting the NMR spectra of mixtures, it is illustrative to discuss the NMR patterns of the pure compounds, for comparison. Figure 1 − .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…To prove that the received product is composed of Ti(OH)OF•0.66H 2 O and TiO 2 (B), we performed XRD measurements and Rietveld refinements of the synthesis product in the past. 12 The results of these measurements can be found in the SI (see Figure S1 and Table S1). The single steps of this synthesis are documented by corresponding photographic images in the Supporting Information of ref 9.…”

Section: ■ Summary and Conclusionmentioning

confidence: 99%

“…10 axis, endowing the compound with interesting electrochemical properties with respect to the incorporation of Li + probably in the channels. 11 In addition to the influence of the IL anion, the length of the alkyl chain of imidazolium-based ILs influences the obtained products as well, 12 allowing us to use just one BF 4 − -containing IL to synthesize Ti(OH)OF•0.66H 2 O instead of a mixture of ILs, contrary to previous studies. 9 Furthermore, within or after the formation of Ti(OH)OF•0.66H 2 O nanoparticles, the polar imidazolium head group attaches on the nanoparticles' surface.…”

Section: ■ Introductionmentioning

confidence: 99%

“…This stabilization effect is more pronounced when using ILs with longer alkyl chains demonstrating how essential the choice of the IL cation is. 12 While thus already several details of the reaction mechanism of the presented IL-based synthesis leading to Ti(OH)OF• 0.66H 2 O and TiO 2 (B) have been clarified, the first steps in the reaction, i.e., involving molecular species, are still unclear. However, the described empirical findings suggest that the final crystal structure is already predetermined at the level of F-and O-containing Ti complexes.…”

Section: ■ Introductionmentioning

confidence: 99%

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Ionic Liquid-Based Low-Temperature Synthesis of Crystalline Ti(OH)OF·0.66H₂O: Elucidating the Molecular Reaction Steps by NMR Spectroscopy and Theoretical Studies

et al. 2022

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We present an in-depth mechanistic study of the first steps of the solution-based synthesis of the peculiar hexagonal tungsten bronze-type Ti(OH)OF·0.66H2O solid, using NMR analyses (1H, 13C, 19F, and 11B) as well as modeling based on density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation. The reaction uses an imidazolium-based ionic liquid (IL, e.g., C x mim BF4) as a solvent and reaction partner. It is puzzling, as the fluorine-rich crystalline solid is obtained in a “beaker chemistry” procedure, starting from simple compounds forming a stable solution (BF4 –-containing IL, TiCl4, H2O) at room temperature, and a remarkably low reaction temperature (95 °C) is sufficient. Building on NMR experiments and modeling, we are able to provide a consistent explanation of the peculiar features of the synthesis: evidently, the hydrolysis of the IL anion BF4 – is a crucial step since the latter provides fluoride anions, which are incorporated into the crystal structure. Contrary to expectations, BF4 – does not hydrolyze in water at room temperature but interacts with TiCl4, possibly forming a TiCl4 complex with one or two coordinated BF4 – units. This interaction also prevents the heavy hydrolysis reaction of TiCl4 with H2O buton the other sidespurs the hydrolysis of BF4 – already at room temperature, releasing fluoride and building F-containing Ti(OH) x Cl4–x F y complexes. The possible complexes formed were analyzed using DFT calculations with suitable functionals and basis sets. We show in addition that these complexes are also formed using other titanium precursors. As a further major finding, the heating step (95 °C) is only needed for the condensation of the Ti(OH) x Cl4–x F y complexes to form the desired solid product but not for the hydrolysis of BF4 –. Our study provides ample justification to state a “special IL effect”, as the liquid state, together with a stable solution, the ionic nature, and the resulting deactivation of H2O are key requirements for this synthesis.

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Section: ■ Results and Discussionmentioning

confidence: 87%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Summary and Conclusionmentioning

confidence: 99%