Owing to the vast diversity of linkers, nodes, and topologies, metal-organic frameworks can be tailored for specific tasks, such as chemical separations or catalysis. Accordingly, these materials have attracted significant interest for capture and/or detoxification of toxic industrial chemicals and chemical warfare agents. In this paper, we review recent experimental and computational work pertaining to the capture of several industrially-relevant toxic chemicals, including NH, SO, NO, HS, and some volatile organic compounds, with particular emphasis on the challenging issue of designing materials that selectively adsorb these chemicals in the presence of water. We also examine recent research on the capture and catalytic degradation of chemical warfare agents such as sarin and sulfur mustard using metal-organic frameworks.
Metal–organic
frameworks (MOFs) have been reported to be
versatile catalysts because of their amenability to modular design
and tunability. Recently, a series of zirconium-based MOFs have been
used to catalyze the hydrolytic destruction of chemical warfare agents
(CWAs) that contain phosphate ester bonds. Here, we adopt density
functional theory calculations to study the hydrolysis of the CWA
simulant methylparaoxon on the Zr-based MOF NU-1000. Our calculated
energy barriers are in quantitative agreement with previous experimental
kinetics data. Comparison between uncatalyzed aqueous hydrolysis and
the MOF-catalyzed reaction reveals the origin of the catalytic effects
of NU-1000 and shows a resemblance to enzymatic catalysis of similar
reactions. The effect of node distortion on the catalytic mechanism
is also examined, and the results are consistent with experimental
findings, where the distorted node of NU-1000 shows an increase in
the rate of methylparaoxon hydrolysis compared to the completely hydrated
regular form of NU-1000.
Recent studies have suggested that the gas-phase hydrolysis of nerve agents by Zr-based metal−organic frameworks (MOFs) may be limited by product inhibition resulting from strong bidentate binding of the hydrolysis products to the Zr 6 -nodes. A potential method to avoid this problem is to deposit single-atom catalysts on the nodes so that the products bind in a more favorable monodentate mode. Such catalytic active sites can be characterized with atomic precision, enabling detailed computational mechanistic studies. Thus, we used density functional theory to perform a comprehensive screening of single-atom transition-metal catalysts, in varying oxidation states, deposited on NU-1000 nodes for the gas-phase hydrolysis of the nerve agent sarin. By calculating the complete reaction pathways for M−NU-1000 systems, we discovered that the highest reaction barrier varies between catalysts, highlighting the need to consider more than a single reaction step when screening a large number of diverse materials. The single-metal catalysts are predicted to exhibit lower product desorption energies than unfunctionalized NU-1000. By comparing their relative turnover frequencies using the energetic span model, we identified several catalysts that are predicted to be more active than the parent MOF for this reaction. Finally, we explored periodic trends and molecular descriptors for their effect on catalytic activity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.