Improved hydrophobicity of ZIF-90 Metal-Organic Frameworks for the removal of fluorinated pollutants from water

Per- and polyfluoroalkyl substances (PFAS) have been widely used in industrial applications due to their high hydrophobicity, and exceptional thermal and chemical resistance. [1] However, these same properties result in their non-biodegradable nature and, consequently, in their accumulation and persistency in the environment with growing concerns on their toxicity to humans and the ecosystem. [2] All these factors explain the current efforts in the study and development of techniques to remove these “forever chemicals” from the environment. In this context, we are focusing on the synthesis and characterization of new Zeolitic Imidazolate Frameworks (ZIFs), as regenerable platforms for PFAS removal from water through adsorption processes. ZIFs features high thermal and chemical stabilities, and within them, ZIF-90 is additionally characterized by bearing an aldehyde group on the imidazole linker, thus opening the way to increasing its chemical tunability trough post-synthetic modification of the porous network via imine condensation. [3] In this contribution I will discuss on the preparation of ZIF-90 with a greener and scalable synthesis, proving that this MOF can be easily and quantitatively obtained in a water-based synthesis at RT and ambient pressure, compared to the solvothermal DMF-based ones reported in the literature. [3] Hydrophobicity and flurophilicity of ZIF-90 has been enhanced through post-synthetic modification with fluorinated hydrazides, to obtain novel adsorbents for PFAS removal from contaminated water. These results will be also thoroughly discussed, together with the adsorption and removal properties of the obtained derivatized materials.