Chemical and Structural Transformations of <i>M</i>–Al–CO<sub>3</sub> Layered Double Hydroxides\n(<i>M</i> = Mg, Zn, or Co, <i>M</i>/Al = 2) at\nElevated Temperatures: Quantitative Descriptions and Effe

Layered double hydroxides\n(LDHs) exhibit diverse chemical compositions\nand are being designed for promising applications such as CO<sub>2</sub> adsorbents. Although many researchers have analyzed CO<sub>2</sub> gas evolution and structural transformation behavior at elevated\ntemperatures, there are still inconsistencies in results on the effect\nof different metal ions in LDHs. In this study, on the basis of atomic/molecular-level\nfindings from our previous study on multistep structural/chemical\ntransformation of Mg–Al LDHs, we analyzed the quantitative\ngas evolution behavior and structural transformations of <i>M</i>–Al–CO<sub>3</sub> LDHs with different divalent metal\nions (<i>M</i> = Mg, Zn, or Co, <i>M</i>/Al =\n2) at elevated temperatures. Our quantitative analysis revealed that\nall three LDH samples undergo the three-step chemical transformations:\nrelease of interlayer water, partial dehydroxylation of the hydroxyl\nlayers, and complete dehydroxylation of layers and decomposition of\ninterlayer CO<sub>3</sub><sup>2–</sup>. However, the temperature\nrange for each step differs, as do the structural transformations\nfor each sample: the layered structure collapses in the first step\nfor Zn–Al LDH and Co–Al LDH, and the third step for\nMg–Al LDH. Our results provide for quantitative and concrete\nunderstanding of the effect of divalent metal ions in LDHs on thermal\ndecomposition.