Design, Synthesis, and Characterization of Metal-Organic Frameworks for Enhanced Sorption of Chemical Warfare Agent Simulants

Metal-organic frameworks (MOFs) and specifically the UiO family of MOFs have been extensively studied for the adsorption and degradation of chemical warfare agents (CWAs) and their simulants. We present a combined experimental and computational study of the adsorption of dimethyl methylphosphonate (DMMP), a CWA adsorption simulant, in functionalized UiO-67. We have used density functional theory (DFT) to design functionalized MOFs having a range of binding energies for DMMP. We have selected three different functionalized MOFs for experimental synthesis and characterization from a total of eight studied with DFT. These three MOFs were identified as having the weakest, intermediate, and strongest binding energies for DMMP of the set, as predicted by our DFT calculations. We find that the order of predicted binding energies agrees with data from temperature-programmed desorption experiments. Moreover, the values of the binding energies are also in good agreement. This serves as a proof of concept that ab initio calculations can guide experiments in designing MOFs that exhibit a higher affinity for CWAs and their simulants. One surprising outcome of this work is that reactions between DMMP and the three functionalized UiO-67 MOFs were not observed under ultrahigh-vacuum conditions for the exposure of DMMP of up to 9000 L. This lack of reactivity is attributed to the low levels of defects in the materials used.