Synthesis and characterization of a layered double hydroxide containing an intercalated nickel(II) citrate complex

The nickel(II) citrate complex anion ([Ni(C6H4O7)]2−) may be intercalated into the interlayer galleries of a layered double hydroxide (LDH) host by a process involving ion-exchange with an Mg2Al–NO3 LDH precursor. The powder X-ray diffraction (XRD) pattern confirms that the layered structure is maintained. The thermal decomposition process of the complex anion-intercalated material has been characterized by in situ high temperature powder XRD, thermogravimetry-differential thermal analysis (TG-DTA) and coupled with mass spectrometry (MS). The thermal stability of the nickel(II) citrate complex anion intercalated in LDHs in air is lower than that in the sodium salt. Calcination generates a high degree of nickel(II) oxide dispersion in a matrix of magnesium and aluminium oxide phases which should be an advantage if the materials are used as catalyst precursors. Based on the observed data, a structural model for the [Ni(C6H4O7)]2− anion intercalated in the galleries of the LDH is proposed.