Highly Selective and Regenerable Pillar[5]arene Polymer for Efficient Removal of Heavy Metals

Heavy metal contamination remains a major global problem. Because these ions are complex to remove and highly harmful to living organisms, efficient and practical remediation methods are urgently needed. Adsorption is one of the most attractive solutions due to its low cost, simplicity, and high removal efficiency. In this work, we developed a sulfur-rich pillararene polymer (Pol-P[5]-EDT) specifically designed to capture Hg2+ and Pb2+ from water. The polymer was synthesized through a straightforward thiol–ene click reaction between an alkenyl pillararene and ethanedithiol. Characterization showed that Pol-P[5]-EDT is amorphous, with a rough, loosely packed morphology and a well-developed hierarchical porous structure. It has a high surface area (391.20 m2/g) and pore sizes mainly around 4.72 and 12.12 nm. Compared with its monomer analogue (Pol-Mono-EDT), the polymer exhibited much better adsorption performance. Adsorption studies revealed monolayer behavior, with maximum capacities of 322.58 mg/g for Hg2+ and 271.23 mg/g for Pb2+. The uptake was extremely fast, removing both ions completely within 5 min. The polymer was also highly reusable, retaining about 99% Hg2+ removal efficiency after five cycles. In a practical test, Hg2+-contaminated water treated with the material allowed wheat seeds to grow normally, demonstrating its effectiveness for real environmental and agricultural applications. The Pol-P[5]-EDT@PES membrane further showed selective current–voltage responses for Hg2+ and Pb2+, indicating potential for sensing as well as removal.