Synthesis and properties of terephthalate and benzoate intercalates of Mg-Al layered double hydroxides possessing varying layer charge

The influence of layer charge on the intercalation of terephthalate and benzoate anions in MgAl layered double hydroxides has been studied. It is found that, under the synthesis conditions used here, incorporation of the anion is dependent upon the Mg:Al ratio of the host sheets. pure terephthalate and benzoate intercalates are formed for a ratio of 2 or less from both chloride and nitrate solutions. At higher values of layer charge competitive incorporation of the counteranion present in the solution (i.e., chloride or nitrate) occurs with decreased incorporation of inorganic anions at ratio 3 or higher. Two extreme orientations are observed for the organize anion within the gallery-either vertical (i.e., perpendicular to the layers) or horizontal. In the case of terephthalate a monolayer arrangement exists, whereas for benzoate the vertical arrangement is a bilayer and the horizontal a monolayer. Whether a vertical or horizontal orientation is adopted depends upon the charge on the layers, the temperature, and the degree of hydration of the sample.