Switchable and highly selective Hg(II) capture enabled by a thermo-responsive MOF-polymer nanohybrid

Mercury (Hg) is a highly toxic and bioaccumulative heavy metal, the chemical-free regeneration of Hg(II) adsorbent is in great demand but remains a challenge, due to the strong binding between Hg(II) and adsorption sites. In this study, a thermally regenerable composites, PDEA-MOF-808, was synthesized by encapsulating the thermo-responsive polymer poly N-[2-(Diethylamino)ethyl]acrylamide (PDEAEAM) within a porous metal-organic framework (MOF-808). The amide and amine functional groups in PDEAEAM, especially the tertiary amine moieties, played key roles in Hg(II) adsorption, achieving a high capacity of 497.5 mg g −1 and rapid equilibrium within 20 min. The composite also exhibited exceptional selectivity (K d  = 3.3 × 10 5  mL g −1 ), leading to high Hg(II) removal efficiencies of over 99.5 % when treating industrial wastewater and natural water. Furthermore, it was efficiently regenerated in warm water at 55 °C within 20 min, maintaining 91.3 % efficiency after ten adsorption-desorption cycles, presenting good reusability and stability. The excellent Hg(II) adsorption performance was attributed to ligand chelation between oxygen- and nitrogen-containing functional groups. This work highlights a sustainable, chemical-free strategy for heavy metal removal and offers a promising approach for developing high-performance, regenerable adsorbent for water treatment applications.