(366e) Effect of Water Loading on the Stability of Dmof-1

An increasingly studied class of adsorbents are metal-organic frameworks (MOFs). Through careful selection of its components, the porosity, surface chemistry, and other physical characteristics of MOFs can be easily tailored. The tunability of MOFs make them attractive candidates for catalysis, sensing, gas separations and storage applications. Unfortunately, some MOFs will degrade in the presence of water vapor, a component found in many chemical process streams. To increase the industrial viability of MOFs, researchers have studied several factors that affect the water stability of these porous materials. However, the relationship between water loading, adsorption temperature, and structural degradation of MOFs has not been explored. To this end, the degradation of the MOF DMOF-1 in water vapor was investigated. Correlations between the amount of water vapor adsorbed by the framework and its ensuing retained surface area and crystallinity were determined through BET surface area measurements, water vapor adsorption at high temperatures, and powder X-ray diffraction. As the quantity of water vapor adsorbed by DMOF-1 increased, degradation from hydrolysis of the MOF worsened. Degradation was attributed to clustering of water molecules in the void space of DMOF-1. Interestingly, it was noted that at a higher adsorption temperature, DMOF-1 was stable under exposure to 80% relative humidity. However, additional NVT Monte Carlo simulations indicate that water molecules cluster in the same way regardless of adsorption temperature. This suggests that DMOF-1 is stable at higher temperatures due to the lower adsorption loading; subsequently, water clusters are less likely to form thereby reducing degradation. These findings demonstrate that MOFs with known stability issues at room temperature could maintain robustness in separations performed at higher adsorption temperatures. Overall, these results highlight the importance of evaluating porous materials at conditions – i.e., temperature, mixture complexity, pressure – that are relevant for the target application.