We noted that gis-ZIF-1 has distinctive structural features unlike previously reported ZIF-6. In detail, ZIF-6 and gis-ZIF-1 have geometrically different CBUs, where 4MRs, Zn4(Im)4, are flattened squares and butterfly tetrahedra, resulting in the difference of space groups -I41/amd (D4h) in ZIF-6 and I41/a (C4h) in gis-ZIF-1, respectively (Figure ). Notably, I41/a space group is a crystallographic subgroup of I41/amd where the reflection symmetry is eliminated and 4MRs have a rotational degree of freedom along 41 screw axes.