A review of removal of per- and polyfluoroalkyl substances using metal-organic framework-based nanoadsorbents

Per- and polyfluoroalkyl substances (PFASs) are a category of extremely persistent environmental pollutants. Metal-organic frameworks (MOFs) have appeared as promising adsorbents for PFAS removal due to their large surface area, tunable porosity, and versatile surface chemistry, which are among the numerous treatment technologies available. This review critically evaluates current developments in the design, fabrication, and application of MOF-based (nano)materials for the adsorption of PFAS in aqueous environments. The adsorption efficacies of MOFs (e.g., pore size, surface charge, and functional groups) and PFASs (e.g., chain length, head group functionality, and polarity) are significantly influenced by their physicochemical properties. The selective and efficient removal of PFASs is governed by the interaction mechanisms such as electrostatic attraction, hydrophobic interactions, H-bonding, and Lewis acid-base coordination. In addition, the adsorption efficacy is significantly influenced by water quality conditions, including pH, ionic strength, background ions, and natural organic matter. Functionalized MOFs (e.g., those with amine, fluorinated, or hydrophobic groups) exhibit resilience to interference, although these factors can sometimes hinder their removal. Both experimental and computational studies have provided valuable mechanistic insights into the rational design of MOFs with improved selectivity and capacity. In addition, this review identifies critical challenges and future perspectives, such as the necessity of standard performance testing under realistic water matrices; the development of scalable, stable, and regenerable MOFs; and their integration into life-cycle assessment and toxicity evaluation.