About MX3 and MX2 (Mn+ = Mg2+, Al3+, Ti4+, Fe3+; Xp− = F−, O2−, OH−) nanofluorides

Alain Demourgues (1) , Nicolas Penin (1) , Damien Dambournet (1) , Romain Clarenc (1) , Alain Tressaud (1) , Etienne Durand (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Several nanosized fluoro-compounds have been prepared by microwave-assisted solvothermal routes: Al3+-, Fe3+- and Ti4+-based oxyfluorides with the hexagonal tungsten bronze (HTB) framework, Ti4+-based fluorinated anatase, and rutile MgF2. The structural features have been determined using XRD and TEM analyses. The presence of OH− groups substituted for F− ions has been demonstrated for all of these nanofluorides. In Al- and Mg-based nanofluorides, the OH rate can be reduced by F2-direct fluorination. Furthermore, the higher the polarizing power of the cation, the higher the oxygen content. For cation with high formal charge, such as Ti4+ stabilized in a distorted octahedral site, the occurrence of O2−/OH−/F− anions in its vicinity as well as vacancies have to be mentioned. Finally coupling the microwave-assisted solvothermal route with the F2-direct fluorination allow preparing high surface area metal fluorides where the amount of oxygen is noticeable and contribute to create under-coordinated cationic species at the surface which can induce high Lewis acidity.

Mots clés: Inorganic fluorides; Nanomaterials; Mixed anions; Microwave synthesis; Structures; Powder XRD

Domaines: Matériaux

Alain Demourgues, Nicolas Penin, Damien Dambournet, Romain Clarenc, Alain Tressaud, et al.. About MX3 and MX2 (Mn+ = Mg2+, Al3+, Ti4+, Fe3+; Xp− = F−, O2−, OH−) nanofluorides. Journal of Fluorine Chemistry, 2012, 134, pp.35-43. ⟨10.1016/j.jfluchem.2011.02.006⟩. ⟨hal-00663171⟩