Zirconia-Pillaring in Layered HNb₃ O₈ and HNbMoO₆

In this work, the pillaring of two layered niobium-based oxides (HNb₃ O₈ and HNbMoO₆ ) with zirconia was investigated in detail. Two novel zirconia-pillared layered metal oxides, zirconia-pillared layered HNb₃ O₈ and zirconia-pillared layered HNbMoO₆ , have been successfully prepared. Both pillared products exhibited a higher thermal stability exceeding 673 K. For the pillaring of layered HNb₃ O₈ , two different pre-expanding agents, 1-dodecanamine and 1,12-dodecanediamine, were alternatively used, and two kinds of zirconium-pillaring solutions containing zirconium(IV) polyoxocations obtained through two different ways were employed. The 1,12-dodecanediamine-pre-expanded layered intermediate was applicable and 1-dodecanamine-pre-expanded one was not applicable to the intercalation of zirconium(IV) polyoxocations in interlayer regions of the layered niobium-based oxides. More interestingly, the zirconium-pillaring solutions prepared by using an appropriate amount of diethylene glycol as stabilizing agent was advantage for constructing the ordered zirconia-pillared product, whereas the zirconium-pillaring solutions obtained in the case of absence of diethylene glycol seemed not to conduct well an ions-exchange reaction with the alkylamine-pre-expanded layered intermediates. The order degree of zirconia-pillared layered transition metal oxides was closely related to the host sheets. The zirconia-pillared layered HNb₃ O₈ contained more defects, while the zirconia-pillared layered HNbMoO₆ had fewer defects.