Ultra-Selective and Efficient Static/Dynamic Palladium Capture from Highly Acidic Solution with Robust Macrocycle-Based Polymers

The capture of palladium from spent nuclear fuel is crucial for the sustainable development of nuclear energy and resource recovery. One of the most challenging issues in this direction is the survival of adsorbents under extreme reprocessing conditions such as strongly acidic media and high radiation fields while still maintaining high extraction ability and selectivity. Herein, an approach to addressing this issue is reported by incorporating macrocycle into nitrogen-rich covalent organic polymers (COPs). Dramatically outperforming current adsorbing materials, pillar[5]arene-based COPs with pyridyl and triazolyl functionalities display record adsorption capacity for Pd(II) at 3 M HNO3 (403 mg g(-1)), extraordinary stability under 500 kGy gamma irradiation, and ultra-high selectivity toward Pd(II) over both 17 coexisting cations and six anions. In particular, the material P5COP-m-BPT with the best performance also shows remarkable dynamic adsorption efficiency for Pd(II). This study not only provides a strategy to enhance all-sided adsorption performance in palladium separation with nitrogen-rich COPs materials but also demonstrates the superiority of customizing advanced materials with macrocycles.