Computational Assessment of CNT–NH₂ and Enzyme-Functionalized Nanomaterials for Polycyclic Aromatic Hydrocarbon Remediation

Polycyclic aromatic hydrocarbons (PAHs) persist in the environment due to their chemical stability, toxicity, and resistance to conventional remediation processes. This study investigates the electronic reactivity and adsorption potential of selected PAHs such as anthracene, benzo[a]pyrene, fluorene, naphthalene, and pyrene using density functional theory (DFT) and molecular docking approaches. Frontier molecular orbital calculations revealed that PAHs with smaller HOMO–LUMO gaps exhibited greater reactivity and more negative Gibbs free energy values, indicating enhanced thermodynamic favorability for adsorption. Benzo[a]pyrene showed the highest reactivity (HOMO–LUMO gap = 7.26 eV) and the most negative Gibbs free energy (–31.80 kcal/mol), suggesting its strong electron-accepting tendency. Binding energy analysis of PAH adsorption onto amine-functionalized carbon nanotubes (CNT–NH₂) further confirmed benzo[a]pyrene as the most strongly adsorbed molecule (E _bind = − 26.75 kcal/mol). Molecular docking of PAHs with a CNT–enzyme ( Bacillus spp . laccase, PDB: 9BD5) complex demonstrated high docking scores and extensive hydrophobic and π–π stacking interactions, indicating a synergistic remediation mechanism driven by nanoparticle adsorption and enzymatic affinity. The combined DFT and Molecular docking results demonstrate that functionalized CNTs coupled with bacterial enzymes offer a highly effective platform for PAH remediation through dual adsorption and catalytic pathways.