Insight into the experiment and extraction mechanism for separating carbazole from anthracene oil with quaternary ammonium-based deep eutectic solvents

• Quaternary ammonium-based deep eutectic solvents (DESs) were synthesized and evaluated for carbazole extraction from anthracene oil, with TBAC:EG (1:2) showing the highest extraction efficiency (85.74%) and selectivity (66.10%). • COSMO-RS predictions of infinite dilution activity coefficients and capacities accurately guided solvent selection, demonstrating strong agreement with experimental results. • The DES TBAC:EG (1:2) was successfully recycled using water as an antisolvent, and its application to real crude anthracene yielded carbazole with 85.32% purity and 60.27% yield. • Mechanistic analysis via σ-profiles and IGMH revealed that hydrogen bonding (N–H...Cl) and van der Waals interactions (C–H...O and C–H...π) are the primary driving forces for carbazole extraction.