## 3 Results and Discussion
### Adsorption Mechanism  
To deduce the adsorption mechanism, FTIR spectra of the CDM-HCP and the CDM-HCP after adsorption of anilines were compared (Figure 10).  
For the FTIR spectra in Figure 10b-e, the broad peak in the region of 3300-3500 cm\({}^{-1}\) was due to the -OH stretching mode of \(\beta\)-CD. The peak intensity weakened slightly and the frequency red-shifted after adsorption of the anilines, implying that there were strong affinities between the CDM-HCP and the anilines. The results demonstrated that the interaction between the functional groups of \(\beta\)-CD with the anilines is formed during the adsorption process. To gain further insight into the adsorption mechanism, Figure 11 shows the changes in the composition of the CDM-HCP before and after adsorption.  
Figure 10: FTIR spectra of the CDM-HCP before and after metal adsorption: CDM-HCP (**a**), CDM-HCP-aniline (**b**), CDM-HCP-\(p\)-MA (**c**), CDM-HCP-\(p\)-CA (**d**), and CDM-HCP-\(p\)-ABC (**e**).  
As shown in Figure 11, the two peaks around 284.7 eV and 532 eV belong to C1s and O1s, respectively. The new peaks of N1s were observed at 400 eV, which may be attributed to the adsorption by anilines, leading to an increase in nitrogen-containing functional groups. The typical C1s XPS spectra of the CDM-HCP with and without adsorbing anilines are displayed in Figure 11b-e. Before adsorption, the peaks at 284.2 and 285.4 eV for the value states of the CDM-HCP were due to the presence of C = C and C-O, respectively. However, a new peak due to C-N appeared at 286.7 eV, which further proves the adsorption of anilines [35]. The discrete Fourier transform (DFT) method was also used to demonstrate that \(\beta\)-CD can form stable complexes with anilines, as shown in Figure S6 (Supplementary Materials). Table S4 (Supplementary Materials) shows the calculated \(BE\) for \(\beta\)-CD/anilines with orientations head down and head up by PM3. The negative binding energies indicated that \(\beta\)-CD could interact with anilines to form stable inclusion complexes. The results calculated by ONiOM2 (B3 LYP/6-31G(d):PM3) also followed the same trend as those from PM3. The \(BE\) from the ONiOM2 calculations for the  
Figure 11: High-resolution XPS spectra of the CDM-HCP (**a**) and C 1s (**b–e**) before and after aniline adsorption.  
\(\beta\)-CD/\(p\)-ABC head down, \(\beta\)-CD/\(p\)-CA head up, \(\beta\)-CD/\(p\)-MA head up, and \(\beta\)-CD/aniline head up were \(-145.79\pm 2.45\), \(-122.47\pm 1.63\), \(-86.09\pm 1.14\), and \(-78.10\pm 0.89\) kJmol\({}^{-1}\), respectively. They showed that stability of the inclusion complexes followed the sequence of \(\beta\)-CD/\(p\)-ABC \(>\beta\)-CD/\(p\)-CA \(>\beta\)-CD/\(p\)-MA \(>\beta\)-CD/aniline, which may lead to the different adsorption capacity. Optimized structures calculated by ONIOM2 also indicated that \(\beta\)-CD can form stable complexes with anilines via the O-H-.-O hydrogen bond, as shown in Figure S7 and Table S5 (Supplementary Materials). It was clear that the significantly enhanced adsorption of anilines on the CDM-HCP was mainly driven by hydrogen bonding between adsorbent and adsorbate. Hydrophobic interactions and \(\pi\)-\(\pi\) stacking attractions also played an important role in the aniline adsorption (Figure 12).