AgI has a higher melting point than vanillin because it is an ionic compound. The bonds are held more tightly together than in vanillin because it is a covalent compound. Ionic bonds have a higher melting point because the electrons are being transferred from one atom to the other.
Silver iodide is an ionic compound and vanillin is a covalent compound. The bonds between atoms are way stronger in ionic compounds, so the melting point is higher in silver.
