Metal-doped graphene as adsorbents for glyphosate: a DFT and molecular dynamics approach

The adsorption of glyphosate on pristine and monodoped graphene was investigated using Density Functional Theory at the PBE-D3/def2-SVP level together with molecular dynamics simulations. Graphene sheets doped with Fe3+, Fe2+, Al3+, Cu2+, Zn2+, Mn2+, Ca2+ and Mg2+ were modeled by substituting a carbon atom in a finite graphene cluster, followed by full geometry optimization in the gas phase. Thermodynamic parameters, including adsorption energy, enthalpy, Gibbs free energy and equilibrium constants, were obtained from vibrational frequency analyses. Fe3+- and Al3+-doped systems exhibited the most favorable interactions, with Gibbs free energy values of −18.69 and −18.88 eV respectively, indicating spontaneous and strong adsorption. Quantum Theory of Atoms in Molecules and Non-Covalent Interaction analyses revealed mixed adsorption character, with contributions from physisorption and localized chemisorption regions in Fe3+ and Al3+ complexes. Molecular dynamics simulations at 298 K over 8 ns showed that doped systems maintained higher structural stability than pristine graphene, as confirmed by root mean square deviation analyses. All simulations were performed in a vacuum to assess intrinsic adsorption properties. This integrated computational approach demonstrates that Fe3+ and Al3+ doping significantly enhances glyphosate binding through cooperative non-covalent and coordinative interactions, highlighting the potential of metal-doped graphene as a rationally designed adsorbent for environmental remediation.