High-efficiency and selective lead capture using thermally regenerable MOF-based adsorbent: Role of thermoresponsive...

The development of innovative materials for selective lead (Pb) capture is crucial, but regeneration research is insufficient, particularly regarding regeneration without chemical reagents. Herein, we introduce a smart, thermally regenerable MOF-based adsorbent for Pb^2 + by incorporating poly(N-isopropylacrylamide) (pNIPAM) and benzo-18-crown-6 ether (B18C6) into MOF-808 (MOF-808-pNB). MOF-808-pNB could capture Pb²⁺ with remarkable removal efficiency (> 99.7 %), ultrafast kinetics (k₂ ∼ 14.95 g mg^-1 min^-1), and outstanding selectivity (K_d > 1.6 × 10⁶ mL g^-1) in multi-ion mixed solutions (e.g., Li⁺, Ca²⁺, Ba²⁺, Cu²⁺, Ni²⁺). Importantly, this material could be easily regenerated at 45°C, showing excellent recyclability (Pb²⁺ adsorption and desorption ∼ 99 % after 10 cycles). Column experiments demonstrated that 1 kg material could treat 3250 L of authentic Pb-contained wastewater to meet drinking water standards (Pb < 0.01 mg/L). Mechanism studies indicate that B18C6 within the material acts as a specific site for capturing Pb²⁺ at 25°C, whereas pNIPAM shrinks thermoresponsively to a hydrophobic state at 45°C. These alterations introduce steric hindrance and repulsion, combined with exothermic properties of B18C6, collectively enabling efficient Pb²⁺ desorption. This work highlights the potential of thermoresponsive MOF-808-pNB for Pb²⁺ removal and provides a reference for the design of stimuli-responsive materials aimed at water purification.