Figure 5.

(a, b) Atomic representation and the primary and secondary networks of ZIF-3 and ZIF-4 structures with mIM ligands, respectively. The corresponding structures with IM ligand have the same primary net and no secondary net. The bulk and shear moduli for ZIF-3 (ZIF-4) are 2.0 and 0.53 (3.1 and 0.80) for IM and 7.8 and 0.96 (7.6 and 1.49) for mIM structures, respectively (values are in GPa). The functional groups of the ligands form a secondary network which enhance the mechanical stability considerably. The primary net is demonstrated with red tubes and secondary net with cyan tubes; white, black, blue, and gray spheres represent H, C, N, and Zn atoms, respectively.