## 3 Results and Discussion
### Acetaldehyde Removal Performance of Functionalized Amine  
In order to increase the acetaldehyde removal capability of CACF-H, an amine functional group using the primary chemical agent of aniline was introduced over CACF-H, where amine can also react strongly with aldehydes [32; 33; 34; 35]. After introducing aniline on the CACF-H (A@CACF-H), all the parameters of pure character were decreased (Table 2) while the N content increased, indicating that the aniline was successfully loaded on the CACF-H surface. \begin{table}
\begin{tabular}{c c c} \hline \hline  & 1 st column & BPX5 (30 m \(\times\) 0.25 mm, 0.25 \(\upmu\)m) \\  & 2 nd column & BPX50 (2 m \(\times\) 0.10 mm, 0.1 \(\upmu\)m) [cut in half] \\  & Over temperature & 90 \({}^{\circ}\)C (1 min) \(\rightarrow\) [1 \({}^{\circ}\)C/min] 230 \({}^{\circ}\)C (0 min) \\ GC \(\times\) GC System & Sample injection mode & Splitless \\  & Sample injection temperature & 300 \({}^{\circ}\)C \\  & Flow & 1.5 mL/min [constant flow] \\  & Modulation time & 9 s \\  & Sample injection amount & 1.0 \(\upmu\)L \\ \hline  & Ionization method & EI+ \\  & Ionization condition & 70 V, 300 \(\upmu\)A \\ TOF-MS system & Ion source temperature & 350 \({}^{\circ}\)C \\  & Acquisition frequency & 50 Hz (0.02 sec/spectrum) \\  & Mass range & m/z 50–700 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: GC \(\times\) GC TOF-MS measurement conditions. The breakthrough curves for the acetaldehyde removal of A@CACF-H with different aniline contents are presented in Figure 2a. All the A@CACF-H samples showed greatly increased acetaldehyde removal capabilities with longer breakthrough times than pristine CACF-H under the given conditions. As expected, removal capability was enhanced by increasing the aniline amount from 1% to 2%, where the 2% content A@CACF-H sample showed the highest amount of acetaldehyde removal among the tested samples. From the data for acetaldehyde removal, provided in Figure 2b, the removal capability of the 2% content A@CACF-H sample was almost 400 times larger than that of the pristine CACF-H, which reveals the effect of the N-functional group on acetaldehyde removal. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{3}{c}{**Elemental Composition (\%)**} & \multicolumn{2}{c}{**Specific Surface**} & \multicolumn{2}{c}{**Average Pore**} & \multicolumn{2}{c}{**Total Pore**} \\ \cline{2-7}  & **C** & **H** & **N** & **O\({}_{\text{diff}}\)*** & **Area (m\({}^{2}\) g\({}^{-1}\))** & **Width (nm)** & **Volume (cm\({}^{3}\) g\({}^{-1}\))** \\ \hline CACF & 86.6 & 0.9 & 0.4 & 12.1 & 1525 & 0.77 & 0.58 \\ CACF-H* & 89.6 & 0.5 & 0.7 & 9.2 & 1368 & 0.81 & 0.55 \\ A@CACF-H & 87.7 & 1.6 & 3.8 & 6.9 & 445 & 1.24 & 0.26 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Elemental composition and porosity characteristics of carbon materials. Figure 2: Comparison of CH\({}_{3}\)CHO adsorption: (**a**) performance and (**b**) calculated removal amounts of CACF-H and A@CACF-H with different aniline concentrations, as well as (**c**) the aniline and acetaldehyde behavior in the micropores of CACF-H when (**a**) uniformly deposited and (**b**) excessively deposited. It is of note that samples with an aniline content above 2% exhibited a drastically reduced acetaldehyde removal capability. Table 3 shows the amounts of aniline that are supported on the CACF-H samples by each aniline-ethanol solution in units of mmol. When the absolute amount of aniline present in a sample was more than 2%, the acetaldehyde uptake amounts decreased from 3.30 to 0.14 mol. This is because excess supported aniline may block the entrance of the micropores, as shown in Figure 2c, which inhibits the physisorption of acetaldehyde and its oxidation reaction. With the optimized amount of aniline, the supporting effect of aniline on removal capability is further confirmed by preparing and evaluating other porous carbons such as QW, MSP-20, and K-C, using the same treatment (Figure 3).