Hydrazone-Linked\nCovalent Organic Framework Catalyst\nvia Efficient Pd Recovery from Wastewater

Global consumption and discharge of palladium (Pd) have\nraised\nenvironmental concerns but also present an opportunity for the sustainable\nrecovery and reuse of this precious metal. Adsorption has proven to\nbe an efficient method for the selective recovery of Pd from industrial\nwastewater. This study investigated a hydrazone-linked covalent organic\nframework (<b>Tfpa-Od</b> COF) as a potential material for the\nhigh-affinity adsorption of Pd<sup>2+</sup> ions from wastewater,\nachieving a <i>K</i><sub>d</sub> value of 3.62 × 10<sup>6</sup> mL g<sup>–1</sup>. The electron-rich backbone of the\nCOF contributes to its excellent selective removal efficiency (up\nto 100%) and adsorption capacity of 372.59 mg g<sup>–1</sup>. Furthermore, the Pd-adsorbed COF was evaluated as a sustainable\ncatalyst for the Suzuki–Miyaura coupling reaction, demonstrating\ngood catalytic conversion and recyclability. This work attempts to\nshowcase a protocol for reusing waste palladium generated in water\nto fabricate heterogeneous catalysts and, thereby, promote the circular\neconomy concept.