Borate pillared layered double hydroxides (LDHs) have been prepared by an ion-exchange method with Mg_0.67Al_0.33(OH)₂(CO₃)_0.165·0.62H₂O being the precursor.The samples were analyzed by XRD, FT-IR, TG-DTA, ICP and 11B MAS NMR.The results showed that by controlling the pH of the ion-exchange medium, borate ions can substitute carbonate ions in the interlayeres.Furthermore, the extent of ion exchange and the nature of the guest ions can be used to control the structure of the products.When the pH of the reaction mixture is 4.5, the interlayer anions are mainly monoborate anions and triborate anions with the plane of the latter being parallel to the layers of the LDHs.Under these conditions carbonate anions are not completely replaced.When the pH value is 3.5, monoborate anions and triborate anions with the plane of the latter being perpendicular to the layers are mainly present in the interlayer galleries.

Key words: LDHs, boric acid, pH, borate-pillared LDHs