By comparing two states of similar densities, it further demonstrates the influence of the system topology on the mechanical properties of ZIF-4 systems. It complements previous results on the high-density states which found the closed-pore ZIF-4 phase bulk modulus (∼ 4.4 to 4.9 GPa) to be much lower than its polymorph ZIF-zni (∼ 14 GPa), while they all show similar densities (1.53 to 1.56 g cm -3 ).