Mechanochemical synthesis of pincer nanotraps for efficient rhodium recovery.

The sustainable recycling of platinum group metals (PGMs) from secondary resources requires task-specific adsorbents that offer both high extraction efficiency and environmental compatibility. However, rhodium recovery remains particularly challenging due to the high thermodynamic stability of its chloro-complexes, which hampers ligand exchange with adsorbent binding sites. Here, we report a series of porous organic polymer (POP)-based nanotraps for targeted rhodium extraction, functionalized with pincer-type chelators, whose installation was realized by mechanochemical imine bond formation in a green, solvent-free manner. Among them, POP-Py-OMe bearing electron-donating –OMe groups, exhibits the highest rhodium uptake capacity and the fastest extraction kinetics from aqueous solution, significantly outperforming its –OH and –H analogues. Furthermore, sequential breakthrough experiments employing various task-specific POPs as column packing adsorbents enable the efficient and selective separation of Pt, Pd, and Rh in sequence with high purity, highlighting a practical and modular strategy for comprehensive PGM recovery. The sustainable recycling of platinum group metals requires task-specific adsorbents that offer both high extraction efficiency and environmental compatibility. Here, the authors report porous organic polymer-based nanotraps for rhodium extraction, functionalized with pincer-type chelators, whose installation was realized by mechanochemical imine bond formation.