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Novel material efficiently removes 'forever chemicals'

University of Utah researchers have developed a material that addresses an urgent environmental challenge: the real-time detection and efficient removal of perfluorooctanoic acid (PFOA), a toxic and persistent member of the PFAS "forever chemicals" family, from contaminated water.

In an industry-funded study in the Journal of Materials Chemistry C, Ling Zang, professor in the College of Engineering's Department of Materials Science and Engineering, and his research team introduced a dual-functional metal-organic framework (MOF) known as UiO-66-N(CH₃)₃⁺, a zirconium-based material known for its thermal and chemical stability.

This new MOF demonstrates exceptional capabilities in both PFOA adsorption and fluorescence-based detection; the MOF literally lights up when it binds to the pollutant, making it easier to quantify the scale of the problem and the rate and efficiency of remediation. The MOF also exhibits excellent reusability, as tested through repeated adsorption–desorption cycles. After each adsorption, the material could be readily regenerated by simple washing.

"This MOF represents a major leap forward for PFAS remediation," said Rana Dalapati, the study's lead author and postdoctoral researcher in the Zang Research Group. "Its ability to both selectively capture and sensitively detect PFOA in real time makes it a versatile and practical solution for water treatment and environmental monitoring."

This work builds on from the Zang lab that created a porous material that fluoresces in the presence of PFAS.

A prominent subset of this group of fluorine-based compounds, PFOA is a synthetic chemical with water and stain-resistant properties and has commonly been used in non-stick cookware, firefighting foam and other products. The material, which does not break down in the environment, has leached into groundwater, raising public health concerns.

Detecting and mitigating PFOA and other PFAS contamination has become a priority for many environmental quality agencies, and Zang's breakthroughs could help.

UiO-66-N(CH₃)₃⁺ features fluorescent tags that turn on once PFOA is captured inside the MOF's molecular cage.

Zang's team constructed their MOF by modifying another widely studied metal-organic framework, known as UiO-66-NH₂, a material recognized for its high porosity and potential in water treatment applications. However, when applied to removal of PFOA, the adsorption capacity of UiO-66-NH₂ is limited due to weak binding interactions.

To address this limitation, the researchers incorporated quaternary ammonium groups that enhance electrostatic interactions with PFOA, resulting in a 3.4-fold increase in adsorption capacity compared to the parent UiO-66-NH₂ framework. These cationic groups also work synergistically with the MOF's metal-binding sites, achieving high selectivity and efficiency in contaminant capture.

The success of this approach underscores the power of post-synthetic modification in MOF design, opening the door to the development of next-generation multifunctional materials with tailored performance for specific environmental contaminants.

Key technological breakthroughs

• Record-High Adsorption Capacity: UiO-66-N(CH₃)₃⁺ achieves a maximum PFOA adsorption capacity of 1178 mg/g, as determined by Langmuir isotherm modeling, far surpassing conventional sorbents such as activated carbon and unmodified MOFs. This sets a new benchmark for PFOA uptake in the field.
• Ultra-Fast Removal Performance: Thanks to its highly porous, interconnected structure, the MOF removes nearly 100% of PFOA from 50 ppb aqueous solutions within 5 minutes. This sort of rapid treatment is crucial for real-world applications.
• High Selectivity and Salt Tolerance: The MOF exhibits strong selectivity for PFOA even in the presence of other PFAS compounds, salts, and natural organic matter, ensuring reliable performance in complex environmental conditions.
• Robust Reusability: The material maintains over 93% adsorption capacity after five regeneration cycles, making it both cost-effective and environmentally sustainable.
• Integrated Fluorescent Sensing for Real-Time Monitoring: Beyond removal, UiO-66-N(CH₃)₃⁺ functions as a highly sensitive "turn-on" fluorescent sensor for PFOA using an indicator displacement assay (IDA). This enables real-time, on-site quantification of PFOA concentrations, offering a user-friendly and rapid alternative to traditional lab-based techniques.