as well as the unloaded (MgCl2) and loaded (MgCl2⋅NH3) sorbent (both solid). Note that in this study only the first of three NH3 sorption steps is considered due to the conditions applied. For all elements in their standard states, i.e. H2, N2 and the inert gases He and Ar, Δ 𝐺° (𝑇) = 0. The standard Gibbs energy of formation of NH3 and MgCl2 is obtained from the NIST JANAF Thermochemical Tables 32 in the temperature range of 0 -6000 K and 0 -900 K, respectively. A polynomial function of fifth order (coefficients see supporting information) is then fitted to the tabulated values to obtain a function of Δ 𝐺° (𝑇).