For all the flow synthesized samples, apart from the Fe HT, increasing aging temperature causes transitions II and III to shift to the lower temperatures, indicating a decrease in thermal stability. Thermal stability is an indicator of strength of Coulomb interactions between cationic layers and anions in-between these layers. We have observed the increase in parameter c upon the increase in the aging temperature, Table . This will reduce the electrostatic interaction between the layers and, thus, would reduce thermal stability for the loss of interlayer anions and water. Hence, we observe the lower temperature shift of transitions II and III in DTG profiles. Depending on composition, the degree of the increase in parameter The fact that the "HT" hydrotalcite with no dopant is the most stable is logical, as substitution within the structure, especially with different size cations, creates disorder and structural changes, as seen from structural analysis of the Fe HT sample by PXRD and Raman. However, thermal stability also depends on the nature of the incorporated cation. For instance, it has been reported that in the cobalt-containing HTs, Co 2+ in the octahedral environment is easily oxidized to Co 3+ during aging or drying stage of preparation, resulting in decreased stability . for M-OH gradually disappear, Figure , indicating collapse of the hydrotalcite structure. Concurrently, the 1042 cm -1 and 1057 cm -1 bands for carbonate ions (high symmetry) shift to 1033 cm -1 and gradually diminish to zero as temperature is increased, see Figure in ESI. This is in agreement with DTG analysis, where the endothermic minimum attributed to carbonate loss is observed at 192 °C, Figure .