Per and polyfluoroalkyl substances, commonly known as PFAS, remain one of the most difficult classes of contaminants to remove from water due to their chemical stability and resistance to conventional treatment methods. In a recent study led by Jun Lou, Professor of Materials Science and Nanoengineering at Rice University, researchers report the development of a light activated material capable of breaking down PFAS along with other persistent organic pollutants. The work adds to a growing body of engineering research focused on destroying contaminants rather than simply separating them from water.
Zhu, Y., Feng, Y., Yan, Y., Wang, Z., Zhang, X., Faraji, S., Ai, Q., Xie, T., Weng, X., Zhou, L., Zhai, T., Liu, Y., Huang, X., Lin, C., Glass, S., Shin, B., Han, Y., Martí, A. A., Ajayan, P. M., … Lou, J. (2025). Covalent organic framework/hexagonal boron nitride heterostructure photocatalysts for efficient degradation of emerging contaminants. Materials Today, 91, 253–260. https://doi.org/10.1016/j.mattod.2025.11.004
The research team designed a hybrid material that combines a covalent organic framework with a two dimensional layer of hexagonal boron nitride. Covalent organic frameworks, or COFs, are crystalline and highly porous polymers that can be engineered for specific chemical functions. Their large surface area and ordered structure make them suitable for photocatalysis, where light energy excites electrons within the material and enables chemical reactions that degrade complex molecules in water.
Jun Lou, Professor of Materials Science and Nanoengineering at Rice University stated,
“These findings show that a single, metal-free material can tackle multiple hard-to-remove pollutants. This moves us closer to practical, low-cost solutions for cleaner water.”
When exposed to light, electrons in the COF are displaced, leaving behind positively charged regions known as holes. The separation of these charges is critical, as it allows reactive species to form at the surface of the material. These species can then attack strong chemical bonds, including the carbon fluorine bonds that make PFAS so persistent in the environment. The hexagonal boron nitride layer plays a key role by helping direct the movement of these charges, reducing energy losses that often limit photocatalytic efficiency.
One of the main engineering challenges addressed in the study was how to bond the COF to the boron nitride surface. Hexagonal boron nitride is chemically stable and typically difficult to modify, which limits its use in hybrid systems. The researchers applied defect engineering by introducing nanoscale imperfections into the boron nitride film. These defects served as reactive sites that allowed the COF to grow directly on the surface, forming a continuous and well connected interface rather than a loose mixture of materials.
This direct growth approach improved charge transport across the interface, allowing electrons and holes to move without becoming trapped. According to the researchers, this configuration enabled the material to degrade not only PFAS but also pharmaceutical residues and synthetic dyes, all without the use of metal based catalysts. Avoiding metals is an important consideration, as metal catalysts can introduce secondary environmental concerns and complicate large scale deployment.
To evaluate whether the material could perform under realistic conditions, the team tested it in flowing water reactors designed to resemble treatment systems used in practice. Both vertical and horizontal flow configurations were examined. The material maintained its structural stability and photocatalytic activity over multiple cycles, suggesting it could tolerate repeated use without rapid degradation.
This work reflects a broader shift in water treatment engineering toward technologies that chemically destroy PFAS instead of capturing and concentrating them. Traditional approaches such as activated carbon adsorption and ion exchange are effective at removal but create waste streams that still require careful disposal. Photocatalytic degradation offers a different pathway by breaking contaminants down into less harmful components.
While further engineering challenges remain, including light delivery in opaque water and long term performance in complex environments, the study demonstrates how interface design at the nanoscale can significantly influence real world treatment performance. As regulatory pressure around PFAS continues to increase, materials that combine stability, scalability, and contaminant destruction are likely to play an increasingly important role in future water treatment systems.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
