## 3 Results and Discussion
### Characterisation
#### 3.2.4 FTIR  
FTIR spectroscopy was carried out to identify the presence of the functional groups for UiO-66, UiO-66-MTX, UiO-66-NH\({}_{2}\), and UiO-66-NH\({}_{2}\)-MTX. The FTIR spectra for UiO-66 and UiO-66-NH\({}_{2}\) were found to be similar to reports in the literature ([PERSON] et al., 2019; [PERSON] et al., 2019; [PERSON] et al., 2020). The symmetrical and asymmetrical stretching of amine generally appears between 3000 and 3400 cm\({}^{-1}\)([PERSON] et al., 2019), which was observed in UiO-66-MTX after MTX loading at 3020 cm\({}^{-1}\), but not in UiO-66. UiO-66 exhibited strong bands at 1585 and 1391 cm\({}^{-1}\), which indicate the asymmetric and symmetric stretching of O-C-O in the BDC linker. The weak band at 1507 cm\({}^{-1}\) is attributed to C=C stretching of the benzene ring, while the band at 1665 cm\({}^{-1}\) demonstrates the C=O stretching in DMF and its presence in UiO-66 pores. No band at 1685 cm\({}^{-1}\) indicates the absence of any free BDC. The bands at 819, 742, and 663 cm\({}^{-1}\) indicate the bending of -OH and O-C-O and the stretching of C=C and C-H bonds in the BDC linker. The FTIR spectrum of UiO-66-MTX provided evidence for MTX loading, as indicated by similar bands at 1638 and 1608 cm\({}^{-1}\) in place of 1640 and 1607 cm\({}^{-1}\) in MTX. This indicates the C=C stretching of alkene and unsaturated ketones. The slight difference in bands can be attributed to the interaction between MTX and UiO-66. A strong band at 1197 cm\({}^{-1}\) revealed the strong C-O stretching of tertiary alcohol of MTX, which was indicated at 1204 cm\({}^{-1}\). A weak band at 970 cm\({}^{-1}\) demonstrates the strong C=C bending of the alkene group (Figure 5A).  
The FTIR spectrum of UiO-66-NH\({}_{2}\) showed bands at 3352 cm\({}^{-1}\) and 3482 cm\({}^{-1}\), which were associated with the symmetric and asymmetric vibrations of the -NH\({}_{2}\) groups, respectively ([PERSON] et al., 2019; [PERSON] et al., 2019). A slight shift in these peaks in UiO-66-NH\({}_{2}\)-MTX suggested a bond formation between MTX and UiO-66-NH\({}_{2}\). The peak at 1648 cm\({}^{-1}\) represented the C=O stretching of DMF and indicated its presence in UiO-66-NH\({}_{2}\) pores. The peak at 1621 cm\({}^{-1}\) in UiO-66-NH\({}_{2}\) showed the stretching vibrations of C-N. Changes in the absorption pattern at 1648 and 1607 cm\({}^{-1}\) in UiO-66-NH\({}_{2}\) indicated the interaction between UiO-66-NH\({}_{2}\) and MTX (Figure 5B).  
Strong peaks of UiO-66-NH\({}_{2}\) and UiO-66-NH\({}_{2}\)-MTX at 1482 and 1368 cm\({}^{-1}\) corresponded to the asymmetric (based on DMF presence) and symmetric stretching of O-C-O and C-N in the BDC-NH\({}_{2}\) ligand ([PERSON] et al., 2019; [PERSON] et al., 2019). A weak band at 1431 cm\({}^{-1}\) attributed to the O-H  
\begin{table}
\begin{tabular}{c c c c} \hline
**MOFs** & **Size (nm)** & **PdI** & **Zeta Potential (mV)** \\ \hline UiO-66 & 156 \(\pm\) 0.4 & 0.279 & 26.7 \(\pm\) 2.23 \\ UiO-66-MTX & 211 \(\pm\) 8 & 0.42 & 19.8 \(\pm\) 0.94 \\ UiO-66-NH\({}_{2}\) & 170 \(\pm\) 2.3 & 0.212 & 30.8 \(\pm\) 0.81 \\ UiO-66-NH\({}_{2}\)-MTX & 487 \(\pm\) 3 & 0.179 & 14.1 \(\pm\) 0.66 \\ \hline \end{tabular}
\end{table}
Table 2: Colloidal properties of UiO-66, UiO-66-MTX, UiO-66-NH\({}_{2}\), and UiO-66-NH\({}_{2}\)-MTX.  
bending in the carboxylic group, while the bands at 803, 761, and 650 cm\({}^{-1}\) indicated a combination of C=C, C-H vibration, O-C-O, and OH bending in the linker. Small changes in these bands in UiO-66-NH\({}_{2}\)-MTX indicated the changes in the chemical environment due to the interaction of MTX and metal ions. The FTIR spectrum of UiO-66-NH\({}_{2}\)-MTX provided evidence for the presence of MTX in the pores of UiO-66-NH\({}_{2}\). The bands at 1382 cm\({}^{-1}\) indicated phenol OH bending of MTX, and 1254 cm\({}^{-1}\) demonstrated C-O stretching of the alkyl aryl ether group.