DFT analysis of fenethylline (Captagon): Investigating its interaction with graphene as a potential adsorbent

Fenethylline, commonly known as Captagon, is a stimulant with amphetamine-like properties that has gained notoriety due to its widespread illicit use, particularly in conflict zones. Its ease of synthesis and environmental persistence necessitate effective remediation strategies. This study investigates the adsorption potential of graphene (G) for Captagon removal using a multi-scale computational approach, including density functional theory (DFT), Monte Carlo (MC), and molecular dynamics (MD) simulations. The interaction between Captagon and graphene was analyzed in both perpendicular and parallel adsorption configurations. The results indicate that the parallel orientation exhibits superior adsorption stability, with an adsorption energy of –51.15 kcal mol⁻1, primarily driven by π–π stacking interactions. Frontier molecular orbital (FMO) analysis further reveals significant alterations in graphene's electronic properties upon Captagon adsorption, with noticeable shifts in the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels and bandgap (Egap). The molecular dynamics simulations confirm the stability of the Captagon-graphene complex, reinforcing graphene's potential as a viable adsorbent. These findings highlight graphene's efficiency in Captagon removal, suggesting its broader applicability in water purification and environmental remediation strategies.