Smart Materials for Dirty Waters: Reversible Aerogels Unlock Closed‐Loop Heavy Metal Remediation for Catalytic Applications

Bio-based catalytic materials are emerging as promising platforms for the development of sustainable chemical processes [1]. In this study, we present a dynamic covalent aerogel derived from chitosan and aldehyde-functionalized lignin, which has been developed as a renewable heterogeneous catalyst with the additional capability to remove toxic metal ions from water [2]. The three-dimensional framework is established through reversible Schiff-base linkages between chitosan and formylated lignin, the latter of which is obtained via a mild Reimer–Tiemann functionalization. Density Functional Theory (DFT) calculations indicate that metal capture is predominantly governed by a tridentate coordination mode. Subsequent to metal uptake, the aerogels can be directly repurposed as recyclable heterogeneous catalysts for cross-coupling reactions. It is noteworthy that these catalysts demonstrate exceptional catalytic performance under mild conditions and in green solvents, thereby enabling the coupling of up to 90% yield. Their straightforward and cost-effective preparation, combined with their pronounced stability, highlights their potential for scale-up and industrial implementation. Furthermore, the reversible nature of the covalent network enables the recovery of the original building blocks and the regeneration of the material, thereby establishing a circular strategy that integrates water remediation with bio-based catalysis.