Materials scientists have developed a material that uses light to break down a range of pollutants in water, including per- and polyfluoroalkyl substances, or PFAS, the “forever chemicals” that have garnered attention for their pervasiveness.
The process involves the use of a class of materials known as covalent organic frameworks, or COFs, whose porous structure—and hence high surface area—make them useful in light-driven, or photocatalytic, reactions. When they interact with light, some of the electrons in COF molecules get displaced, forming holes, and this bifurcation of charges is what makes COFs good photocatalysts.
According to a study in Materials Today, the Rice team grew a COF material directly onto a two-dimensional film of hexagonal boron nitride (hBN), giving rise to a hybrid supercleansing surface that needs only light in order to cut through tough pollutants, including pharmaceutical waste, dyes, and PFAS.
“By combining two safe, lightweight materials in a new way, we built a powerful pollution-fighting surface that works quickly, works on many different pollutants and does not rely on metals that could harm the environment,” says Yifan Zhu, a postdoctoral researcher in Rice’s material science and nanoengineering department and a first author on the study. “This matters because it offers a cleaner, cheaper, and more sustainable way to protect our water.”
To construct this surface, the researchers had to find a way to combine the two materials, which are usually difficult to attach to one another. They did so using defect engineering, a technique that deliberately embeds defects or imperfections into a material in order to engender new properties or behaviors. In this case, the team etched microscopic “scratches” into the hBN surface. The imperfections served as reactive sites anchoring the COF to the hBN film and enabling it to grow directly on top. The resulting interface directs the light-energized electrons and holes in different directions, creating the cleansing effect.
“By growing them directly together rather than simply mixing them, we created a connected structure where charges could travel easily without getting trapped,” Zhu says. “This approach had not been done before with this pair of materials, especially because hBN is usually very hard to modify.”
To examine performance under practical conditions, the team tested the material in vertical and horizontal flowing-water reactors—mirroring equivalent setups in water treatment facilities. The material performed consistently over repeated cleansing cycles, maintaining structure and stability.
“These findings show that a single, metal-free material can tackle multiple hard-to-remove pollutants,” says Jun Lou, a corresponding author on the study and a professor of materials science and nanoengineering. “This moves us closer to practical, low-cost solutions for cleaner water.”
Additional researchers from Rice and the University of Florida contribute to the work.
The research was supported by the National Science Foundation ; the Air Force Research Laboratory International Research, Innovation and Science in Nanotechnology (RISING) Center at Rice; and the Welch Foundation. The content in this press release is solely the responsibility of the authors and does not necessarily represent the official views of funding organizations and institutions.
Source: Rice University
