As an example, the frameworks of SU-102, SU-105 and SU-106 all with ZrO8 square antiprism coordination polyhedra, are each composed of different Zr(EA)4 isomers. To systemically classify and distinguish the isomers, we have considered two factors: 1) the pairing of the phenolic oxygen vertices around the ZrO8 site, and 2) the orientations of the four ellagate ligands.