Abstract
•COFs remove PFAS through combined electrostatic and hydrophobic interactions.•Two-dimensional COFs capture PFAS in minutes while 3D COFs require hours.•COFs perform well even in complex water matrices with ions and natural organic matter.•Future needs: multi-functional COFs with easy regeneration and cheaper synthesis.
Poly- and perfluoroalkyl substances (PFAS) have been detected in water sources worldwide, raising significant public health concerns due to their potential toxicity to humans. This review examines covalent organic frameworks (COFs), crystalline, stable porous organic polymers synthesized in two-dimensional (2D) and three-dimensional (3D) structures, for PFAS removal from water. The review evaluates the effectiveness of COFs with different functionalities in removing both long-chain and short-chain PFAS. Studies have shown that 2D COFs demonstrate faster adsorption kinetics (minutes) than 3D COFs (hours). The review discusses the influence of COF pore size, functional groups, and environmental water parameters on PFAS removal. The adsorption mechanism primarily involves electrostatic and hydrophobic interactions. However, unlike conventional adsorbents such as activated carbon and ion exchange resins, COFs offer distinct mechanistic advantages, including: (1) precisely tunable pore architectures that can be tailored to PFAS molecular dimensions, (2) the ability to incorporate multiple binding sites within a single framework through strategic functionalization, (3) faster adsorption kinetics due to ordered crystalline channels, and (4) synergistic capture mechanisms, where both the COF backbone and functional groups contribute to PFAS binding.Studies of PFAS removal in natural waters have shown that inorganic ions and natural organic matter minimally influence removal efficiency. The path forward lies in developing multi-functional COFs with enhanced stability and smart regeneration triggers. These include photo-responsive COFs that can be regenerated through UV or visible light exposure, thermo-responsive frameworks allowing low-temperature regeneration (40–60 °C), and pH-switchable COFs that release PFAS under mild pH adjustments. Practical implementation requires addressing several interconnected challenges. Cost-effective synthesis routes using cheaper building blocks and greener conditions are essential for commercial viability. Equally important is scaling up production from laboratory to industrial quantities while maintaining structural integrity and performance.The translation of batch processing to continuous flow systems presents significant engineering hurdles, particularly in terms of framework stability under prolonged use, pressure drops across packed beds, and effective separation of spent materials from treated water. Despite these challenges, the exceptional performance of COFs for PFAS remediation, particularly for short-chain PFAS that are difficult to remove with conventional methods, positions these materials as promising candidates for next-generation water treatment technologies.