Per- and polyfluoroalkyl substances (PFAS) pose significant challenges in water treatment due to their persistence, mobility, and the limitations of conventional sorbents. Recent advancements highlight electrochemical separations as a promising strategy for water purification, offering modularity, scalability, and the potential for net-zero emissions when integrated with renewable energy sources. However, the widespread adoption of electrochemical methods is often limited by insufficient ion-rejection and low selectivity, leading to increased energy demands. To overcome this challenge, the development of tailored materials with molecular-level selectivity is essential for enhancing separation efficiency and reducing energy consumption. Fluorinated materials offer a promising approach for PFAS separation through fluorophilic interactions. This study investigates the role of fluorinated copolymer chain length in PFAS adsorption and desorption, combining molecular dynamics (MD) simulations with experimental electrochemical adsorption studies. Integrating redox-active and cationic functional groups with fluorophilic groups, we can increase the uptake capacity towards short-chain PFAS (C < 7). We find that PFAS binding is governed not by co-monomer chain length but by the total fluorophilic interactions available. However, the length of fluorinated side chains influences polymer packing and porosity, affecting PFAS capture and release mechanisms. Simulations reveal that short-chain PFAS percolate into polymer pores, whereas long-chain PFAS aggregate on the surface, enabling faster desorption. Leveraging these insights, we develop functional electrodes for PFAS separation, demonstrating enhanced desorption upon applying potential, achieving over 80% electrode regeneration. Additionally, we assess the impact of fluorinated co-monomer chain length on separation factors (SF), achieving SFs of 190 for perfluorooctanoic acid (PFOA, 7 C-F) over perfluorobutanoic acid (PFBA, 3 C-F). These findings provide critical design principles for fluorinated materials in PFAS separation, with implications for sustainable water treatment and industrial purification processes.
