Why Do Carbonate Anions Have Extremely High Stability in the Interlayer Space of Layered Double Hydroxides? Case Study of Layered Double Hydroxide Consisting of Mg and Al (Mg/Al = 2)

Layered double hydroxides (LDHs) are promising compounds in a wide range of fields. However, exchange of CO 3 2– anions with other anions is necessary, because the CO 3 2– anions are strongly affixed in the LDH interlayer space. To elucidate the reason for the extremely high stability of CO 3 2– anions intercalated in LDHs, we investigated in detail the chemical states of CO 3 2– anions and hydrated water molecules in the LDH interlayer space by synchrotron radiation X-ray diffraction, solid-state NMR spectroscopy, and Raman spectroscopy. We found the rigidity of the network structure formed between the CO 3 2– anions, hydrated water molecules, and the hydroxyl groups on the metal hydroxide layer surface to be a crucial factor underlying the stability of CO 3 2– anions in the LDH interlayer space.