Exfoliation of α-Zirconium Phosphate Using Tetraalkylammonium Hydroxides

alpha-Zirconium phosphate (alpha-ZrP), a classical layered compound, has found widespread application. Exfoliation of alpha-ZrP has been mainly achieved by propylamine (PA) or tetrabutylammonium hydroxide (TBAOH), but the exact mechanism of exfoliation has not been completely elucidated. We examined the feasibility of exfoliation utilizing tetraalkylammonium hydroxide (TXAOH) and investigated the stepwise intercalation/exfoliation mechanism of alpha-ZrP. All of the TXAOHs examined (carbon number of the branches: 1-4) were able to exfoliate alpha-ZrP in an aqueous dispersion under ultrasonication. Furthermore, exfoliation of alpha-ZrP by two different exfoliators (either a mixture of two or sequentially) was also investigated to pinpoint the exfoliation mechanism. Our results indicate that small TXA cations are kinetically preferred to diffuse into the galleries of alpha-ZrP, while large TXA cations can help open up the galleries and facilitate transport of the already intercalated cations. These findings should help fellow researchers to choose the most suitable exfoliators for their own projects and develop better intercalation/exfoliation systems.