One-pot epoxide-driven synthesis of M₂Al(OH)₆Cl·1.5H₂O layered double hydroxides: Precipitation mechanism and relative stabilities

A family of single-crystalline particles of M₂Al(OH)₆Cl·1.5H₂O layered double hydroxides (LDH) with M(II) a transition-metal cation were obtained by a one-pot room-temperature homogeneous alkalinization driven by glycidol ring opening. In contrast with traditional homogeneous methods, LDH phases are obtained in the exchangeable chloride-containing form. The main precipitation steps were assessed by continuous measurement of pH profiles, field emission scanning electron microscopy, and powder X-ray diffraction, revealing the heterogeneous nucleation of LDH phase over previously formed nano-Al(OH)₃ seeds. The precipitation pH plateau of each LDH follows the trend of the inherent solubility of the single M(II) phases obtained under alkalinization. A linear free-energy relation links the solubility of the bare M(II) hydroxides with the correspondent M(II)-Al(III) LDH, in good agreement with previously reported thermochemical models.