Neodymium (Nd) and dysprosium (Dy) are essential components of high-performance permanent magnets used in renewable energy systems and electric vehicles. Global demand for these rare earth elements (REEs) is rising, while primary deposits are limited and concentrated in a few countries. Their frequent co-occurrence in REE sources and nearly identical ionic radii make separation particularly challenging. Therefore, ensuring sustainable Nd/Dy supply chains has become a critical global priority. This study introduces a novel ligand for selective Nd/Dy separation from coal fly ash leachates, an abundant and underutilised secondary REE resource in India. The modified di-(2-ethylhexyl) phosphoric acid (D2EHPa) ligand replaces conventional alkyl chains with naphthyl groups and incorporates an oxalate functionality. These structural changes enhance TT-electron interactions and introduce an additional chelation site, fundamentally altering the coordination environment compared to unmodified D2EHPa. Density functional theory (DFT, Gaussian 16) simulations reveal stronger binding energies and more negative Gibbs free energy (aG) values for Dy(III) than Nd(III). This predicted Dy selectivity can be leveraged to reduce the number of solvent extraction stages in industrial circuits, lowering reagent consumption, operational costs, and environmental impact. Computational screening of ligand-metal interactions also identifies promising candidates before synthesis, reducing experimental failure rates and accelerating the development cycle. Such advances can make REE recovery from secondary sources commercially viable, supporting the adoption of circular resource use in critical minerals processing. Future work will explore nitrogen donor group incorporation into the naphthyl-oxalate framework, evaluated through combined computational and experimental methods. The approach aligns with India-australia collaboration opportunities, combining India's large-scale secondary REE feedstocks with australia's expertise in REE separation. Potential outcomes include ligand synthesis, laboratory and pilot-scale trials with real leachates, joint research, knowledge exchange, and potential co- development of intellectual property. This research supports sustainable, diversified, and sovereign REE supply chains by linking molecular-level design to industrial application.