Atomically dispersed iron-decorated activated carbon for boosted adsorption of oxygenated/chlorinated volatile organic compounds

Oxygenated and chlorinated volatile organic compounds (OVOCs/CVOCs), which are widely emitted from fuel storage and solvent applications, require effective adsorption and recovery strategies to enhance resource utilization efficiency. In this study, Fe-modified activated carbons (ACs) were prepared via two distinct methods: adsorption and impregnation. Adsorption-based modification of AC facilitated equilibrium-driven Fe 3 + complexation on functional groups, resulting in atomically dispersed Fe. In contrast, the impregnation method induced rapid hydrolysis of Fe species during solvent evaporation, which promoted localized Fe accumulation. The adsorption performances and mechanisms toward representative OVOCs and CVOCs were investigated. Results demonstrated that 0.6 %Fe(A)/AC prepared through the adsorption method exhibited enhanced adsorption capacities for methanol and dichloromethane by 48 % and 28 %, respectively, under dry conditions compared to pristine AC. Remarkably, 0.6 %Fe(A)/AC maintained superior adsorption performance at 60 % relative humidity compared to other samples. The atomic-level dispersion of Fe atoms facilitated the high dispersion of coordinated hydroxyl groups, which inhibited collective hydrogen bonding with H 2 O molecules and mitigated the rapid formation of water clusters. Conversely, Fe species agglomeration in 5.5 %Fe(I)/AC prepared through the impregnation method caused significant performance deterioration at 60 % relative humidity. Theoretical calculations demonstrated that Fe atoms deposited on AC exhibited high adsorption energies for both OVOCs and CVOCs. Moreover, hydrolysis-derived hydroxyl groups bound to Fe functioned as supplementary active sites, further enhancing adsorption capacity. This work provides theoretical and technical insights for designing efficient OVOC and CVOC adsorbents.