DFT Investigation of Layer-Parity-Driven V-Based MXene Nanosheets for Uremic Toxin Adsorption: Implications for Wearable Artificial Kidney Applications

Patients with end-stage renal disease (ESRD) rely on dialysis for survival; however, conventional dialysis cannot fully replicate normal kidney functions, often leading to serious long-term complications. Wearable artificial kidneys (WAKs) represent a promising alternative, but their development is critically limited by the efficient removal of uremic toxins such as urea and creatinine. In this study, first-principles density functional theory is employed to systematically investigate the adsorption behavior of these two clinically relevant toxins on two-dimensional (2D) oxygen-terminated V-based MXenes, V n C n–1 O 2 (n = 2–5), with a particular focus on the role of transition-metal layer parity. Owing to their high surface-to-volume ratio, these 2D nanomaterials provide abundant active sites for adsorption, a pronounced layer-parity effect is also observed, wherein odd-layer MXenes (V 3 C 2 O 2 and V 5 C 4 O 2 ) consistently exhibit stronger adsorption than even-layer counterparts. Urea shows significantly higher adsorption energies (up to ∼−1.3 eV), characteristic of chemisorption driven by localized interfacial charge redistribution and hydrogen bonding, whereas creatinine adsorption is weaker and dominated by polarization-driven physisorption despite exhibiting larger net Bader charge transfer. Combined charge density, Bader charge, and density of states analyses reveal that strong adsorption correlates with localized electronic interactions rather than the magnitude of total charge transfer. Comparison with Ti-based MXenes reported in the literature further indicates that V-based MXenes intrinsically possess a more adsorption-active electronic structure. These findings highlight the importance of layer parity in such nanomaterials and thereby help in designing efficient adsorbents and identifying odd-layer V-based MXenes as promising candidates for selective uremic toxin removal in wearable artificial kidney applications.