Theoretical study on activation mechanism of fluorine substitution reactions of Keggin-MAl₁₂ in aqueous solutions

Abstract

The fluorine substitution reactions of Keggin polymeric aluminum species K-MAl₁₂ (M = Al, Ga, Ge) were investigated using density functional theory. Two substitution pathways (associative and dissociative) were simulated. The results show that the replacement of charged tetrahedral center metals causes the change in energy barrier either for associative mechanism or dissociative mechanism. The preferred activation mechanisms are proposed by comparing associative and dissociative barriers for fluorine substitution reactions of three Keggin Al species. The fluorine substitution reactions of Al₁₃ and GaAl₁₂ are inclined to dissociative mechanism and GeAl₁₂ follows an associative mode, indicating a mechanistic variation induced by the alteration of tetrahedral metals.

Keywords:

• Fluorine substitution reaction
• activation mechanism
• Keggin-MAl₁₂

Acknowledgements

Further support is acknowledged from Anhui Provincical Key Laboratory for Degradation and Monitoring of Pollution of the Environment.