A historical overview of the activation and porosity of MOFs including strategies to design and preserve permanent porosity in MOFs.

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Chemical warfare agents (CWAs), such as sarin and sulfur mustard, continue to be a threat due to their high toxicity coupled with worldwide usage. Metal–organic frameworks (MOFs) are efficient materials for the adsorption and detoxification of CWAs because of their high porosity and tunable reactivity. MOFs can be utilized as adsorbents designed to have high uptake of these compounds, allowing time for the degradation of the CWAs into benign moieties. In this study, ten Zr MOFs differing in surface area/pore volume, secondary building unit (SBU) connectivity, pore functionalization, and open metal sites were examined for the adsorption of sarin gas and 2-chloroethyl ethyl sulfide, a sulfur mustard simulant. We observed the CWA loading across the series of MOFs to elucidate the significance of each factor on the capture of the substrates. High surface areas/pore volumes and increased hydrogen-bonding interactions were influential toward the increased uptake of both GB and CEES. Because of the presence of more active sites per unit volume, UiO-66, defective UiO-66, and MOF-808 were found to have the highest reactivities toward GB. With the results obtained from this study, different topologies can be utilized based on the targeted application.

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Metal–organic frameworks (MOFs) NU-1000 and UiO-66 are herein exposed to two different gamma irradiation doses and dose rates and analyzed to determine the structural features that affect their stability in these environments. MOFs have shown promise for the capture and sensing of off-gases at civilian nuclear energy reprocessing sites, nuclear waste repositories, and nuclear accident locations. However, little is understood about the structural features of MOFs that contribute to their stability levels under the ionizing radiation conditions present at such sites. This study is the first of its kind to explore the structural features of MOFs that contribute to their radiolytic stability. Both NU-1000 and UiO-66 are MOFs that contain Zr metal-centers with the same metal absorption cross section. However, the two MOFs exhibit different linker connectivities, linker aromaticities, node densities, node connectivities, and interligand separations. In this study, NU-1000 and UiO-66 were exposed to high (423.3 Gy/min, 23 min, and 37 s) and low (0.78 Gy/min, 4320 min) dose rates of 60Co gamma irradiation. NU-1000 displayed insignificant radiation damage under both dose rates due to its high linker connectivity, low node density, and low node connectivity. However, low radiation dose rates caused considerable damage to UiO-66, a framework with lower aromaticity and smaller interligand separation. Results suggest that chronic, low-radiation environments are more detrimental to Zr MOF stability than acute, high-radiation conditions.