In contrast, for those materials with a low heat capacity (red and yellow dots), the heat requirement reduces by as much as 50% and make these the top performing materials. In fact, using the actual values of the heat capacity changes the ranking completely compared to using a constant value (see Figure ). Particularly for materials with a similar range of CO 2 uptake, the value of the heat capacity is prominent. For example, the ranking correlation is almost lost when we look at the materials with similar CO 2 uptake: the ones with lower heat capacity appear to be performing considerably better. As the heat capacity used in the previous studies 14 was significantly above the average, many of these studies have overestimated the energy requirements; for some materials as much as 50%. As these energy requirements contribute significantly to the cost of the capture process, our results can have significant practical impacts.