National Sciences Foundation

The Cook Lab (University at Buffalo)

The continued introduction of PFASs into the environment and their persistence, including the degradation products formed during advanced chemical treatment has raised public concern. While some technologies have emerged to remove or destroy PFASs, these treatment systems are either energy inefficient or laborious to synthesize/perform, making them impractical for large-scale use. Based on a previous study from Fulong et al. using an iron-based metallacage to remove PFASs, this current work builds upon the removal of PFASs using a zirconium-based metallacage.

Metallacages were chosen due to their self-healing capabilities and lack of permanent covalent bonds. Metal-organic frameworks can lock in impurities or errors when synthesized, but a self-assembling metallacage can be produced by crystallization, where new bonds are not formed, and any errors can be fixed via the self-healing feature. Furthermore, discrete metallacages can have porosity behavior that can be switched on or off, which is useful for reuse of the cage. Zirconium was chosen as a base for the metallacage due to its high porosity among other metallacages. This, combined with studies that show similar zirconium metallacages having high resistance to temperature and pH, leads us to believe that a zirconium-based cage will be a good choice for our goals. Metallacages have been applied to a myriad of projects, such as biomedical uses, catalysts, host-guest chemistry, and small molecule transport. Because of the specialization of these metallacages through the use of different ligands, the versatility of the self-assembling metallacage will be used to optimize removal of PFASs from water samples.

The self-assembly method involves mixing in building blocks that are designed to align into specific, discrete structures. Because the building blocks are made to lead into a specific design, the resulting complexes are relatively pure and very stable. Hence, a simplified synthesis with fewer steps, which fits the needs of a PFAS-removal method on an industry (such as wastewater treatment) or environmental remediation level may be possible to achieve. The goal of this project is to investigate several preparations of self-assembled metallacages that can be used to capture multiple classes of PFASs with fast kinetics and high capacity, using multiple ligands.

Overall objectives:

1. Synthesis of a metallacage to achieve quick removal of PFAs in water samples

2. Diffusion and binding kinetics experiments to determine rates of binding and method of capture for the metallacage

Recent Related Publications:

1. Fulong, C., Guardian, M. G., Aga, D. S., Cook, T. (2020). A Self-Assembled Iron(II) Metallacage as a Trap for Per- and Polyfluoroalkyl Substances in Water. Inorganic Chemistry. 59.