## 3 Results and Discussion
### 2D GC TOF-MS Results  
The results of 2D GC TOF-MS analysis before and after adsorption of 2% A@CAVF-H under a relative humidity (RH) of 40% are shown in Figure 4, with a summary of their molecular identifications provided in Tables 4 and 5. This detailed molecular information can be used to predict the reaction mechanisms that occur during the adsorption process. Based on the summarized molecular identifications, it may be speculated that the reaction between acetaldehyde and the amine functional group occurs via two reaction pathways. First, acetic acid oxidized by the acetaldehyde may react with the amine functional group to form an amide species (2, 3, and 4 in Figure 4). In the case of aniline (Figure 4), a stronger aniline peak (No. 3) is observed before acetaldehyde removal compared to the other substances. This intensity decreased by more than 3 times, which was calculated by the GC-MS, showing aniline content reduction from 320 mg/L to 51 mg/L, comparing before and after the acetaldehyde removal test. In contrast, various produced amide species, such as N-phenyl-formamide, N-phenyl-glyoxylamide, and N-phenyl-acetamide, were detected after the acetaldehyde removal test. Second, 2-methyl-quinoline can be produced though a reaction between amine and the aldol condensates of acetaldehyde. The reaction pathway for the formation of 2-methyl-quinoline may follow the Skraup-Doebner-Von Miller or Mannich reactions (Figure 5) [36,37]. In the case of a Skraup-Doebner-Von Miller reaction, an aldol condensation of acetaldehyde is catalyzed by the supported amine, which usually occurs in the micropores. The formation of 2-methyl-quinoline through the Skraup-Doebner-Von Miller reaction [36,37] is shown in Figure 5. In the case of the Mannich reaction, the acetaldehyde reacts with aniline to form an imine structure. Some of the acetaldehyde converts to a more stable state of vinyl alcohol (CH\({}_{2}\)=CH-OH). The quinoline formation reaction then occurs. Others can be suggested in terms of the N-species, both from the CACF-H itself and the column materials of the GC system. Therefore, the formation of amide species and 2-methyl-quinoline from acetaldehyde over the adsorbent can be described as the main behavior. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Value** & **Name** & **Formula** & **Match** & **CAS \#** & **Molecular Weight** \\ \hline \textbackslash{} & 276194 & 2-Chloronicotinitrile & C6H3 ClN2 & 529 & 6602-54-6 & 138 \\ \textbackslash{} & 4607653 & Carbamoyl chloride, phenyl- & C7H6 ClNO & 711 & 2040-76-8 & 155 \\ \textbackslash{} & 45761364 & Aniline & C6H7N & 845 & 62-53-3 & 93 \\ \textbackslash{} & 985755 & 4-amino-N-t-butyloxycarbonyl-, & C18H28N2O4 & 512 & 0-00-0 & 336 \\ \textbackslash{} & & t-butyl ester & & & \\ \textbackslash{} & 1872067 & Methanamine, & C9H11N & 611 & 6907-71-7 & 133 \\ \textbackslash{} & 868060 & o-Chloroxaniline & C6H6 ClN & 628 & 95-51-2 & 127 \\ \textbackslash{} & 570027 & m-Chloroxaniline & C6H6 ClN & 617 & 108-42-9 & 127 \\ \textbackslash{} & 2831315 & Propanedintrile, & C6H6N2O & 682 & 123-06-8 & 122 \\ \textbackslash{} & 46303 & 1H-Pyrrole, 2-phenyl- & C10H9N & 663 & 3042-22-6 & 143 \\ \textbackslash{} & 1194857 & Quinoline, 2-methyl- & C10H9N & 837 & 91-63-4 & 143 \\ \textbackslash{} & 4887046 & Pyridine, & C7H10N2 & 790 & 6627-60-7 & 122 \\ \textbackslash{} & 538737 & Bis(2-chlorophenylothy)ethylamine & C6H13 Cl2N & 670 & 538-07-8 & 169 \\ \textbackslash{} & 407290 & Methanamidamide, & C13H12N2 & 771 & 622-15-1 & 196 \\ \textbackslash{} & 554214 & 9-Hexadecenoic acid & C16H30O2 & 752 & 2091-29-4 & 254 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Detected chemical species from 2% of A@CACF-H before De-CH\({}_{3}\)CHO test. Chemical species were extracted by the CDCl\({}_{3}\). Figure 4: GC \(\times\) GC TOF-MS spectra of 2% of A@CACF-H before and after De-CH\({}_{3}\)CHO test (extraction solvent: CDCl\({}_{3}\)). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.