Heteropore-Mediated Pore-Environment Tuning in a Covalent Organic Framework for Balanced Capture of Structurally Diverse PFAS

Abstract

The rational design of framework adsorbents for structurally diverse contaminants requires pore environments that can accommodate different molecular scales while preserving strong host–guest interactions. Here, we report a heteroporous covalent organic framework (COF) in which hierarchical pore architecture and local chemical functionality are jointly tuned through multicomponent reticular synthesis. The optimized ET-F1BIm5-iCOF integrates cationic and fluorinated motifs into a crystalline micro/mesoporous scaffold. In this architecture, mesopores facilitate molecular accessibility and transport, enabling rapid capture, whereas the smaller pores provide confined local environments that, together with the mixed cationic and fluorinated functionalities, can provide favorable binding environments for short-chain PFAS, helping compensate for their weaker hydrophobic driving force. This integration of heteroporosity and complementary chemical functionality distinguishes the material from adsorbents that rely primarily on surface area or isolated binding groups and provides a pore-level design principle for balancing accessibility, confinement, and interaction strength. Using perfluorooctanoic acid (PFOA) and hexafluoropropylene oxide dimer acid (GenX) as representative PFAS compounds spanning conventional long-chain and emerging short-chain chemistries, ET-F1BIm5-iCOF exhibited rapid adsorption kinetics and high capacities, reaching 903 and 673 mg g–1, respectively. Spectroscopic analyses together with DFT calculations and molecular dynamics simulations support the cooperative contributions of electrostatic recognition, fluorinated/hydrophobic interactions, and heteropore confinement to PFAS binding. Incorporation of the COF into a chitosan aerogel further enabled continuous-flow PFAS removal in ultrapure and river water matrices. This work provides a hierarchical pore-engineering strategy for developing framework materials toward contaminants with different molecular sizes, geometries, and interaction requirements.