## 4 Conclusions  
In this study, we investigated the mechanism for the adsorption of CH\({}_{3}\)Cl, CS\({}_{2}\), C\({}_{2}\)H\({}_{6}\)S, and C\({}_{6}\)H\({}_{6}\) onto activated carbon modified with pyridine and pyrrole functional groups by analyzing ESP and non-covalent interactions. The polarity of the activated carbon surface is enhanced through the incorporation of nitrogen-containing functional groups. Upon the introduction of the pyridine functional group, a negative ESP surrounds the pyridine nitrogen, leading to a decrease in the absolute ESP on the activated carbon plane. Conversely, when incorporating the pyrrole functional group, a positive ESP is observed on the hydrogen atom connected to the pyrrole nitrogen, resulting in an increase in absolute ESP on the activated carbon plane. The physical adsorption of CH\({}_{3}\)Cl and CS\({}_{2}\) on the activated carbon plane is influenced by the ESP of the activated carbon plane. The presence of a pyrrole functional group enhances the adsorption capacity of CH\({}_{3}\)Cl and CS\({}_{2}\) on the activated carbon plane, whereas the pyridine functional group has limited or even unfavorable effects. The S atom in C\({}_{2}\)H\({}_{6}\)S plays a crucial role in the adsorption process by forming dispersion interactions with C atoms on the activated carbon plane and hydrogen bonds with H atoms at the edges. Both pyridine and pyrrole functional groups positively impact the adsorption of C\({}_{2}\)H\({}_{6}\)S, with pyrrole exhibiting a more significant promotion effect than pyridine. The adsorption of C\({}_{6}\)H\({}_{6}\) onto activated carbon occurs through parallel-displaced \(\pi\)-\(\pi\) stacking interactions, where the influence of the pyrrole functional group is minimal while the pyridine functional group weakly promotes it. Moreover, it should be noted that VOCs exhibit higher adsorption energy on the activated carbon plane compared to that at its edges, indicating a greater propensity for their adsorption onto it. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14051793/s1](https://www.mdpi.com/article/10.3390/app14051793/s1)]([https://www.mdpi.com/article/10.3390/app14051793/s1](https://www.mdpi.com/article/10.3390/app14051793/s1)), Figure S1: Molecular models of activated carbon and volatile organic compounds (VOCs): (a) NF, (b) PD, (c) PR, (d) CH\({}_{3}\)Cl, (e) CS\({}_{2}\), (f) C\({}_{2}\)H\({}_{6}\)S, and (g) C\({}_{6}\)H\({}_{6}\). Typical bond lengths (A) have been marked with text; Figure S2: IGMH analysis diagram depicting the adsorption of CH\({}_{3}\)Cl on different activated carbon surfaces: (a,d) NF plane, (b,e) PD plane, (c,f) PR plane, and (g) PD edge. Atoms are colored by \(\delta\)G\({}^{\rm atom}\). Bond critical points (orange spheres) and bond paths (brown lines) are also shown. Electron density values (a.u.) at the bond critical points are indicated by texts. Figure S3: IGMH analysis diagram depicting the adsorption of CS\({}_{2}\) on different activated carbon surfaces: (a) NF plane, (b) PD plane, (c) PR plane, (d) NF edge, and (e) PD edge. Atoms are colored by \(\delta\)G\({}^{\rm atom}\). Bond critical points (orange spheres) and bond paths (brown lines) are also shown. Electron density values (a.u.) at the bond critical points are indicated by texts. **Author Contributions**: Methodology, Y.Z., S.Z. and X.R. ; Formal analysis, Q.S. ; Investigation, S.X. and L.Y. ; Resources, F.C. ; Writing--original draft, Y.Z. and S.Z. ; Writing--review and editing, X.R., R.W. and N.M.; Supervision, Q.S., R.W. and N.M.; Funding acquisition, Y.Z. ; Conceptualization, S.Z. and X.R. ; Validation, S.X. and L.Y. ; Software, F.C. ; Project administration, Q.S. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was financed by the Shandong Provincial Natural Science Foundation of China (Grant No. ZR2021 QE293). **Data Availability Statement:** Data are contained within the article.