Catalysis-Mediated, Ion-Size Modulation-Driven Separation of Transition Metal Complexes

Critical minerals have become integral to modern society due to their indispensable applications in energy, defense, construction, electronics, medicine, and other sectors. However, their limited availability and susceptibility to supply chain vulnerabilities make the extraction and separation of these minerals an important area of research. Among these critical minerals are tantalum and niobium, transition metals with invaluable applications in aerospace, energy, construction, and medical imaging. These minerals have very similar physical and chemical properties and almost always occur together in nature as oxide ores, making their separation using conventional approaches challenging and resource-intensive. In this study, we employ density functional theory, ab initio molecular dynamics, and machine learning simulation methods to explore the use of catalytically active 2D membranes, called MXenes, in separating these minerals. Our approach utilizes catalytic reactions to separate the fluoro-complexes of tantalum and niobium (formed by dissolving the oxide ore in hydrofluoric acid), which have similar physical properties in solution. The catalytic process dissociates the ionic complexes to yield modified complexes with distinct physical properties. By leveraging these differences, we observed faster translocation rates for tantalum complexes through nanopores in the 2D membrane. Further analysis shows that these distinct physical properties result in different interactions between the nanopore wall and the dissociated ionic complexes, leading to varying translocation barriers, which explain the different flux rates. Overall, this work establishes a catalysis-driven route for separating mineral complexes with nearly identical properties, offering a fundamentally different approach to critical mineral separation.