Water uptake via the formation of water clusters in ZSM-5 at temperatures below 125 °C will increase the heat capacity of the zeolite sample. This is not accounted for in either set of simulated ΔTMax values, which continue to increase with decreasing temperature down to the lowest temperature measured. In contrast, the experimental temperature jump magnitudes diminish at these lower temperatures. An estimate of the zeolite heat capacity (Cp) from experimental ΔT values can be obtained through use of Eq 3 (with details of this calculation given in ESI Section 16). These estimated Cp values match those from Lu et al. used in the simulations at T ≥ 125 °C (Figure ). At lower temperatures, these estimates are up to 250% of the value predicted for the zeolite alone, indicating that water clusters within the zeolite raise the heat capacity of the sample. The fact that the difference in predicted and experimentally-estimated Cp values is so large suggests that this difference in heat capacities is likely to be responsible for the majority of the deviation from simulated heating behaviour observed experimentally below 125 °C.