Since their first use during World War I, chemical warfare agents (CWAs) have periodically been used throughout the 20<sup>th</sup> and 21<sup>st</sup> century to cause harm to both military personnel and civilians. Recently, some zirconium-based members of the class of porous, crystalline materials known as metal-organic frameworks (MOFs) have demonstrated efficient catalytic degradation of CWAs. Our lab has developed a high-throughput screening (HTS) method to rapidly and reliably analyze a large amount of materials for the degradation of the CWA simulant dimethyl-4-nitrophenyl phosphate (DMNP). With this tool we have reported large libraries of Zr-MOFs, namely the UiO-66 series (UiO = University of Oslo), with varying functional groups to develop structure activity relationships (SARs). In this talk, we will discuss libraries of MOFs with varying functional groups (MTV UiO-66 and halogenated UiO-66 MOFs) and describe how these functional groups have improved the catalytic properties of the MOF. Theoretical calculations on these materials, in particular the iodine functionalized UiO-66-I MOFs suggest that this increased hydrolysis rate occurs as a result of halogen bonding between the iodine atom and the DMNP molecule making the phosphorous center more electrophilic. Building from these results, we set out to synthesize a UiO-66 MOF containing a pseudohalogen functional group to increase the activity of the MOF against CWAs while also providing a reactive handle for polymerization of the material to more easily implement MOFs into textiles. This led to the synthesis of UiO-66-NCS (NCS = isothiocyanate) via postsynthetic modification (PSM). We screened UiO-66-NCS for the degradation of DMNP using our HTS method and found it displayed ~20-fold higher activity than unmodified UiO-66 at pH = 8. The reactive isothiocyanate handles on the MOF provide an opportunity to polymerize the MOF into thiourea based networks. We have shown that this MOF-PTU mixture can be used for coating of textile fibers using a spray coating technique. The covalently bound UiO-66-NCS particles adhere much better to the textile fabric than a series of control MOFs bringing these materials significantly closer to an industrially applicable process. In short, this talk will highlight both the improvement of MOFs as catalysts through functional group derivatization and the incorporation of these materials into polymer-based textiles for personal protective equipment (PPE) against CWAs.

MOFs and MOF-polymer hybrid materials for the degradation of chemical warfare agents

ACS Fall 2021

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