Theoretical investigation into the interaction mechanism of hexavalent americium with covalent organic framework (PyN-DAB)

Abstract

The separation of radionuclide americium (Am) is a crucial challenge in the reprocessing of spent nuclear fuel, due to the complex speciation. Selective coordination of hexavalent americium [Am (VI)] with covalent organic frameworks (COFs) has emerged as a promising strategy to address this issue. In this work, we employed first-principles simulations combined with density functional theory (DFT) to investigate the adsorption stability of COF (PyN-DAB) for the linear americyl ion AmO22+. Our results demonstrate that COFs can effectively and stably coordinate with Am (VI), highlighting their potential for Am separation. Furthermore, we explored the high-oxidation-state model of AmO22+ complexes with the PyN-DAB ligand to elucidate the underlying microscopic interaction mechanisms between AmO22+ and the PyN-DAB monomer. Comprehensive analyses revealed a strong attraction between the PyN-DAB and AmO22+, which is attributed to the synergistic effects of electrostatic interactions, orbital interactions, and π-electron-rich aromatic rings within the PyN-DAB framework. These findings not only provide fundamental insights into the Am separation process but also offer a novel perspective on the potential applications of COFs in the efficient extraction of actinides. Thus, this study contributes to the ongoing efforts to develop advanced materials for nuclear fuel reprocessing and waste management.