## 3 Results and Discussion
### Theoretical Analysis of the Water Dissociation Reaction Rate
\begin{table}
\begin{tabular}{c c c} \hline \multicolumn{3}{c}{**Binding Energies of Reactant and Products Inside Zn-MOF-74**} \\ \hline Functional & Zn Metal Center E\({}_{\text{b}}\) (eV) & Organic Linker E\({}_{\text{b}}\) (eV) \\ \hline MeOH & \(-\)0.780 & DNB \\ H\({}_{2}\)O & \(-\)0.612 & \(-\)0.610 \\ OH & \(-\)2.442 & DNB \\ H & \(-\)2.002 & \(-\)1.932 \\ \hline \end{tabular}
\end{table} 
Table 2: Calculated binding energies (in eV) of reactants and products to both the Zn metal center and the organic linker prior to and after water dissociation for a methanol/water mixture. DNB indicates that the functional did not bind. Figure 3: Schematic of Zn-MOF-74 interacting with (**a**) methanol/D\({}_{2}\)O assisting the reaction by the formation of clusters in a similar fashion as pure D\({}_{2}\)O; (**b**) isopropanol/D\({}_{2}\)O hindering the interaction of D\({}_{2}\)O with the secondary carbon in the IPA molecule due to the steric barrier; (**c**) pure deuterated water (D\({}_{2}\)O) and cluster formation; and (**d**) He/D\({}_{2}\)O, with He obstructing water cluster formation. White, yellow, red black, blue and purple spheres represent H, D, O, C, Zn, and He atoms. Each schematic has a normalized Zn-MOF-74 IR spectra after 8 h of reaction at 180 \({}^{\circ}\)C.  
exchange MeOH \(\rightarrow\) MeOD. The disappearance of the 1003 cm\({}^{-1}\) mode in Figure 2b thus indicates that more and more MeOH gets converted into MeOD (1060 cm\({}^{-1}\)) via the mechanism discussed above. Isopropyl alcohol, on the other hand, slows down the dissociation reaction over time (Figure 1b), similarly to what is observed for the He/D\({}_{2}\)O mixture (Figure 3d), suggesting that steric interactions are important in the case of IPA. We previously reported that inert gases such as He and Ar block the intermolecular interactions between water molecules by disrupting the formation of water clusters (networks), thus effectively increasing the reaction barrier [14]. Similarly to noble gases, IPA prevents water cluster formation, even at much lower pressure than noble gases, thus slowing down the dissociation rate. In contrast to methanol that fosters the reaction, the size of IPA prevents reaction more than the propensity of its OH group to react with the metal site, as discussed below. Note that the chemical and crystalline structures of MOF-74 remain after D\({}_{2}\)O/alcohol exposure (see Figure S7). In summary, the experimental results supported by computational analysis suggest the reactions illustrated in Figure 3 (with reaction pathways simulated for 1 vs. 4 water molecules reacting with 1 MeOH molecule is presented in Supplementary Materials in Section S4). Methanol by itself has a higher steric hindrance than water, but not high enough to block the reaction given the overall pore size in MOF-74. Because the reaction is experimentally observed to take place at high temperature, dissociation of methanol is favored; as a consequence of MeOH's stronger interaction with the metal center, the reaction achieves a more stable final state (Table 2). After interacting with the metal center, MeOH and D\({}_{2}\)O molecules form an organized structure (cluster), which helps to reduce the dissociation reaction barrier of D\({}_{2}\)O at the organic linker--and the reaction proceeds as outlined above. Steric obstruction of water clustering due to a bulkier alcohol, such as isopropanol, is presented in Figure 3b. The \(-\)CH\({}_{3}\) groups surrounding the secondary carbon block water molecules from clustering and reduce the dissociation rate by 40% in comparison to pure D\({}_{2}\)O as presented in Table 1. Note that a lower pressure (8 Torr) of IPA is needed than He gas (950 Torr) to reduce the water dissociation rate to the same level, suggesting co-adsorbing IPA is an effective way to suppress water dissociation and therefore to increase the MOF stability for gas uptake and other applications. Further details are presented in the supplementary information in Section S5.