The influence of intrapore cation on the fluorination of zeolite Y

The influence of the intrapore cation on the fluorination of zeolite Y from dilute fluoride solutions has been studied, revealing fluoride reacts with the zeolite framework in the presence of a Brønsted acid to form [SiO3F] and [AlO3F] moieties. 29Si{1H} Cross-polarised MAS NMR indicates the reaction proceeds by the substitution of surface hydroxide moieties for fluoride. The fluorination reaction is strongly influenced by the nature of the intrapore cation. Intrapore Brønsted acids facilitate fluorination of the framework by in situ ion-exchange, releasing the acidic ions to the zeolite surface. The fluorination reaction may be further promoted by the presence of intrapore alkaline earth cations (viz. Mg2+, Ca2+, Sr2+ and Ba2+). The conclusions of this work are significant to the preparation of fluorinated zeolite catalysts, the application of zeolites in defluoridation and the labelling of zeolite-based tracers with 18F for application in positron imaging techniques. [Display omitted] •Essential role of Brønsted acids on zeolite fluorination has been established.•Fluorine containing moieties in fluorinated zeolites revealed by 19F MAS NMR.•Likely mechanism of zeolite fluorination established using 29Si{1H} CP MAS NMR.•Promoting effect of divalent metal cations on zeolite fluorination established.