Hydrazone-Linked Covalent Organic Framework Catalyst via Efficient Pd Recovery from Wastewater

Global consumption and discharge of palladium (Pd) have raised environmental concerns but also present an opportunity for the sustainable recovery and reuse of this precious metal. Adsorption has proven to be an efficient method for the selective recovery of Pd from industrial wastewater. This study investigated a hydrazone-linked covalent organic framework (Tfpa-Od COF) as a potential material for the high-affinity adsorption of Pd²⁺ ions from wastewater, achieving a K_d value of 3.62 × 10⁶ mL g^-1. The electron-rich backbone of the COF contributes to its excellent selective removal efficiency (up to 100%) and adsorption capacity of 372.59 mg g^-1. Furthermore, the Pd-adsorbed COF was evaluated as a sustainable catalyst for the Suzuki-Miyaura coupling reaction, demonstrating good catalytic conversion and recyclability. This work attempts to showcase a protocol for reusing waste palladium generated in water to fabricate heterogeneous catalysts and, thereby, promote the circular economy concept.