Beta-blockers are widely prescribed pharmaceuticals used to manage cardiovascular conditions such as hypertension, arrhythmias, and post-heart attack recovery. Among them, atenolol (ATL) and metoprolol (MTL) are particularly common. Their high chemical stability benefits therapeutic efficacy but also means they degrade slowly, persisting in the environment. Conventional wastewater treatment plants are largely ineffective at removing these compounds, allowing them to enter rivers and lakes, where even low concentrations can exert chronic toxic effects on algae, fish, and other aquatic organisms.
To remove such persistent pharmaceuticals, researchers have explored the development of advanced adsorbent materials, such as covalent organic polymers (COPs). These porous materials can be engineered with diverse functional groups, allowing fine tuning of adsorption properties. Recently, COPs incorporating fluorine atoms have gained significant attention for their unusually high adsorption performance and consequently, potential for removing environmental pollutants. Yet, few studies have explored their application in removal of pharmaceuticals.
Filling this gap, a research team led by Professor Yuhoon Hwang from the Department of Environmental Engineering at Seoul National University of Science and Technology (SeoulTech), investigated FCOPs as adsorbents for beta-blockers. "Our study shows that FCOPs are very promising for removing persistent beta-blockers from water," says Prof. Hwang. "We also clarified the adsorption mechanisms that explain why FCOPs achieve unusually high adsorption capacities." The study was made available online on July 28, 2025, and published in Volume 285, Part 3, of the journal Environmental Research in November 15, 2025.
The team prepared a FCOP using a simple, catalyst-free one-pot method and tested their ability to remove ATL and MTL from water. Remarkably, FCOPs demonstrated outstanding adsorption performance, removing 67.3% of MTL and 70.4% within the first minute. Interestingly, when the researchers plotted its adsorption performance against beta-blocker concentration, the curve showed a sigmoidal or S-shaped profile.
At lower concentrations, adsorption increased gradually, consistent with the monolayer adsorption effect, where molecules get adsorbed onto the adsorbent surface in a single layer. However, beyond a concentration of 60 mg/L, the uptake rose sharply for both beta-blockers, indicating a multilayer adsorption effect. In multilayer adsorption, molecules stack in multiple layers, and their interactions can enhance adsorption performance. This adsorption behaviour sets FCOPs apart from traditional adsorbents. Importantly, the FCOP maintained this strong adsorption performance even in real water samples containing multiple ions and organic acids.
The team also identified the key mechanisms driving this unusually high performance. They found that the rich structure of FCOP, consisting of abundant fluorine atoms, leads to multiple synergistic interactions. First, the presence of fluorine leads to strong intermolecular interactions between FCOP and beta-blockers. Second, electrostatic interactions play a key role in adsorption of the positively charged beta-blockers onto the negatively charged FCOP molecules. Finally, the hydrophobic nature of FCOP minimizes contact with the water, promoting the aggregation of adsorbed molecules, facilitating multilayer adsorption.
"These synergistic interactions comprehensively explain the outstanding adsorption capacity of FCOP. Our findings could serve as a valuable foundation for designing next generation adsorbents," remarks Prof. Hwang. "In future, these fluorine-rich adsorbents will be valuable in reducing pharmaceuticals in aquatic environments, not only protecting aquatic life, but also ensuring safer drinking water.
By integrating FCOPs into advanced treatment systems, water utilities could more effectively mitigate pharmaceutical pollution. This innovation represents a significant step toward sustainable purification strategies that safeguard ecosystems and human health.
