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Figure 1
Inorganic SBUs (Secondary Building Units) of various coordination numbers are known in the family of the zirconium-based MOFs (a–d). The SBUs of MOF-520 (e) and MOF-519 (f) have the same number of framework BTB linkers (represented in grey), however, in the former, formate ligands are incorporated while additional BTB ligands (represented in orange) are found in the latter. Blue balls and polyhedra represent the metal atoms (Zr in a–d, Al in e and f), black and orange balls are C atoms, and red balls are O atoms.

IUCrJ
Volume 1| Part 6| October 2014| Pages 563-570
ISSN: 2052-2525
doi:10.1107/S2052252514020351