Facile synthesis of pure phase γ-AlOOH and γ-Al₂O₃ nanofibers in a recoverable ionic liquid via a low temperature route

Mesoporous γ-AlOOH and γ-Al₂O₃ with fibrous morphology were successfully synthesized by an ionic liquid ([OMim]Br) assisted low temperature precipitation method using aluminum nitrate and ammonia as aluminum source and precipitant, respectively. The samples were characterized by XRD, TG, FT-IR, TEM, and N₂ adsorption-desorption technique. The results showed that the concentration of [OMim]Br had a significant effect on the phase, porous structure, and morphology of γ-Al₂O₃ due to the strong interactions between [OMim]Br and γ-AlOOH. High purity γ-AlOOH was synthesized at 0.2 M [OMim]Br and γ-Al₂O₃ with a specific surface area of 243.53 m² g^-1, pore volume of 0.68 cm³ g^-1, and average pore size of 11.10 nm was obtained after calcination. Furthermore, the recyclability of [OMim]Br was investigated. The recovery rate of [OMim]Br could reach 95.0 wt%, and the recycled [OMim]Br still had effects on the synthesis of γ-AlOOH and γ-Al₂O₃.