Metal organic frameworks (MOFs) and functionalized MOF derivatives for PFAS remediation from water: synthesis strategies, removal performance, and mechanisms

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulating pollutants that pose serious threats to environmental and human health. Traditional remediation agents have lower selectivity for PFAS, especially for short-chain PFAS. Thus, tailoring adsorbents is essential for selective removal of short- and long-chain PFAS, even in complex environmental settings. However, functionalizing non-crystalline and amorphous materials is challenging and unpredictable; performance varies due to their heterogeneous structural and functional properties at the molecular level. Alternatively, metal-organic frameworks (MOFs) are highly crystalline and porous materials that can be functionalized in a well-defined manner compared to non-crystalline materials. Thus, functionalized MOF-based adsorbents or degradation agents have emerged as intriguing next-generation platforms for PFAS remediation, owing to their extraordinarily high surface area, customizable pore structures, and tunable surface properties. In this review, recent breakthroughs in synthesis, functionalization, and environmental application of MOFs for PFAS removal from wastewater systems were highlighted. Special focus is given to amino-functionalized, cationic, hydrophobic, fluorophilic, and MOF-derived hybrid composites that promote effective PFAS remediation. Adsorption mechanisms of PFAS removal via electrostatic attraction, hydrophobic partitioning, hydrogen bonding, pore filling, and fluorine–fluorine interactions were explored. In addition, the catalytic degradation of PFAS by MOF-based systems via advanced oxidation, photocatalysis, persulfate activation, and reactive oxygen species (ROS) generation is briefly discussed, including recent progress and limitations, such as incomplete defluorination and byproduct formation. Issues of hydrolytic stability, metal leaching, regeneration, scalability, and environmental safety of MOF-based remediation agents are reviewed. Emerging techniques, such as integrated adsorption-degradation systems, are proposed to accelerate the practical deployment of MOF-based technologies. Finally, a brief comparative review of MOFs with other remediation agents, such as activated carbon, biochar, clay minerals, commercial resins, and covalent organic frameworks (COFs), is presented. The advantages and limitations (e.g., potential risks) of the MOF-based adsorbents were highlighted from theoretical and practical application perspectives. This review provides recommendations for the rational design of next-generation MOFs for wastewater treatment applications.