Reversible Aerogels for Heavy-Metal Capture and Reuse as Cross-Coupling Catalysts

Water remediation technologies urgently require materials that are sustainable, efficient, and regenerable. In this study1, we present a dynamic covalent aerogel derived from chitosan and formylated lignin that combines heavy metal adsorption with post-use catalytic functionality. The aerogel is formed through reversible imine bonds between chitosan and aldehyde-functionalized lignin, synthesized via a mild Reimer–Tiemann reaction2. The resulting monoliths exhibit high structural integrity, solvent tolerance, and pH resistance (pH ≥ 7), together with remarkable adsorption capacities toward Cu²⁺, Pb²⁺, and Zn²⁺ ions (up to 32.8 mg g⁻¹). Density Functional Theory (DFT) calculations indicate that tridentate coordination is the dominant binding mode responsible for metal sequestration. Beyond remediation, the metal-loaded aerogels can be repurposed as efficient, recyclable heterogeneous catalysts for cross-coupling transformations under mild, green conditions, delivering high yields over multiple cycles. Finally, the dynamic covalent network enables complete component recovery and material regeneration, establishing a closed-loop strategy that integrates sustainable water detoxification with circular, bio-based catalysis.