The possible structures in which square SBUs (such as the paddle-wheel) are linked by identical links are derived from four-connected nets in which there is a planar (or near planar) vertex arrangement where all links are equivalent (quasiregular).¹¹ Replacing the vertices by (in the present report) a square of vertices is a process which we have called augmentation.^10e In the case of polyhedral structures the augmentation process is usually called truncation, and there are three possibilities¹¹ for square units:  The truncated octahedron with 6 squares, the truncated cuboctahedron with 12 squares, and the truncated icosidodecahedron with 30 squares. We have previously used 1,4-benzenedicarboxylate (BDC) with 180° (straight) links to produce an infinite periodic structure.^10c The analogous 1,3-benzenedicarboxylate (m-BDC) with 120° between functional groups is ideal for building a finite truncated cuboctahedron structure with 12 linked paddle-wheels. Here we have used this design principle toward the synthesis of large discrete molecular units.

We report the synthesis of a porous metal−organic polyhedron Cu₂₄(m-BDC)₂₄(DMF)₁₄(H2O)₁₀·(H2O)₅₀(DMF)₆(C2H5OH)₆, hereafter termed a-MOP-1 (a = anorthic = triclinic) which is constructed from 12 paddle-wheel units bridged by m-BDC to give a large metal−carboxylate polyhedron.