Figure 5: XRD on the thermal structural dynamics of a)ZIF-62-a and silver-doped ZIF-62 structures b)AgZIF-62-a, c)AgZIF-62-b, and d)AgZIF-62-c. Ag peak marked with asterisk (*), and ZIF-zni peak marked with hash (#).
A dynamic study of the thermal effects of Ag-doped ZIF-62 crystals was performed using in-situ thermal XRD in Figure 5 to further understand the structural changes in Ag-doped ZIF-62. For a lower bIm ratio, Ag nanoparticles start to form at a temperature of between 150 oC to 200oC. It is also interesting to note that ZIF-zni was formed for a lower bIm ratio and at a much lower temperature of below 200 oC than that previously reported for ZIF-4 and ZIF-62 via recrystallization [30,31]. ZIF-zni is a dense form of the imidazolate (Im) based ZIF and the presence of benzimidazolate (bIm) ligand usually prevents its formation due to the bulkier ligands preventing the complete collapse of the frameworks. The temperature of ZIF-zni formation here is close to the AgNO3 melting point, which may indicate that the AgNO3 molecules were mobilized at this temperature and started to interact with bIm in the structure. This caused the rearrangement of imidazole parts to form a ZIF-zni structure. However, at a higher bIm ratio, ZIF-zni formation was not observed, and the glass was able to be melted fully and become fully amorphous with Ag nanoparticle present. This shows that the Ag in the structure may have interacted with bIm in the structure during heating, leading to these observable changes. As the formation of ZIF-zni is seen in both AgZIF-62-a and AgZIF-62-b, future analysis will be only focused on AgZIF-62-a and AgZIF-62-c to compare and understand the interactions and functionality of ZIF-zni-forming and glass-forming AgZIF-62.