As mentioned in the main text, other work has looked at the N-M (where M is one of Mg, Mn, Fe, Co, Ni, Cu, or Zn) bond strength as an indicator of the location of the step pressure in the isotherm . A weaker bond allows for easier separation of the N and M atoms, thereby enabling CO 2 chemisorption at lower partial pressures. Shaidu et al. point out that there is more nuance here, and that the binding enthalphies do not tell the whole story, and entropic effects must be included as a correction to the enthalpies, à la Gibbs free energy, are necessary for this description to fully correlate with the experimental data.