Infrared spectroscopy (IR) can be employed to characterise the di?erent chemical bonds in a material and to identify the functional groups present. The comparison IR spectra of ZIF-8 with 2-methylimidazole (MeIM) and ZIF-67 with 2-methylimidazole (MeIM) is shown in Fig. 6 28. It was reported that most of the absorption bands of ZIF-8 and ZIF-67 are akin to the vibrations of the 2-methylimidazole units, such as the peak at 1584 cm-1 , which is attributed to the C=N stretch mode, whilst the vibration bands at 1350–1500 cm-1 are attributed to the imidazole ring stretching.
The vigorous bands at 1150 and 995 cm-1 is due to the C-N stretching of the imidazole units, weak peaks at 2930 cm-1 and 3138 cm-1 (assigned to C-H stretch). A vigorous and broadband on 2-methylimidazole, elongating over the frequency range 2500 and 3000 cm-1 (attributes to the H?N···H hydrogen bridge), and the N?H stretch vibration appears again at 1843 cm-1, which is completely disappeared on the synthesized ZIF-8 and ZIF-67 29,30,31