DFT investigation of dye adsorption on pristine and doped graphdiyne: toward efficient removal of disperse yellow 3 from wastewater.

The persistence of industrial dyes such as Disperse Yellow 3 (DY3) dye in wastewater remains an environmental concern due to their chemical stability and toxicity. Graphdiyne (GDY), a two-dimensional (2D) carbon-based material, offers a promising platform for adsorption owing to its porous structure and extended π-conjugation. However, its pristine-GDY form exhibits limited binding performance. To enhance its interaction with pollutants, silicon (Si) and germanium (Ge) doping were introduced. This study employs Density Functional Theory (DFT) to examine the adsorption behavior of DY3 dye on pristine, Si-doped, and Ge-doped GDY under both vacuum and aqueous conditions. Four optimized configurations which are parallel, side-parallel, carbonyl-linked, and carbon-linked were analyzed in both pristine and doped models. The results show minimal changes in adsorption energy and geometry in water, confirming the structural integrity of the systems under realistic conditions. Electronic structure analyses including Density of States (DOS), the Natural Bond Orbital (NBO), molecular orbital studies (HOMO-LUMO), infrared (IR) and Reduced Density Gradient-Non-Covalent Interaction (RDG-NCI) visualizations reveal enhanced charge transfer, reduced energy gaps, and distinguishable physisorption and chemisorption features upon doping. Among all models, Si-GDY in the carbonyl-linked configuration exhibits the highest binding energy (-6.00 eV), indicating its superior stability. Additionally, thermodynamic parameters were calculated, revealing improved adsorption performance in doped systems. Non-covalent interaction analysis further confirmed the role of electrostatic, electronic, and charge transfer interactions in stabilizing dye adsorption. These findings demonstrate that doped GDY, particularly Si-GDY, offers enhanced adsorption efficiency, making it a promising candidate for environmental remediation involving persistent dye pollutants.