Adsorption was chosen as the means to introduce silver ions into the
ZIF-62 structure as it is one of the more straightforward methods to
incorporate ions into porous structures. While some MOF encapsulation
methods involve a one-pot in situ encapsulation during the synthesis of
MOF, this method was not incorporated in this paper as the impact of
silver ions on the formation of ZIF-62 during the normal synthesis route
has not been studied well and will add complications which fall outside
the scope of this study - which is to understand the role of silver ions
towards the dynamics of ZIF-62 thermal behaviour. Methanol was also
chosen as the adsorption medium, both to dissolve silver ions and to
disperse ZIF-62 crystals, even though silver ions (from
AgNO3 for this study) are much more soluble in aqueous
conditions. This is because ZIF-62 crystals are highly hydrophobic and
will not disperse well in water. A less toxic alternative such as
ethanol was not chosen due to the possibility of the formation of an
explosive byproduct when reacted with AgNO3, such as the
highly explosive silver fulminate[28]. The
as-synthesized ZIF-62 particles were activated overnight before silver
adsorption to ensure that the pores were effectively vacant to maximize
the silver adsorption efficiency. The morphology of the crystal between
pure and silver-loaded ZIF-62 glass at different benzimidazole -
imidazole ratio as seen in Figure 2 also shows that there was no clear
morphological change in the shape of the resulting crystals.