Research on microporous structures has concentrated largely on inorganic materials such as aluminosilicates and aluminophosphates. 1 The assembly of microporous materials from organic molecule and metal ion building blocks is an emerging area that is yielding new generations of open supramolecular architecture. 2 An important strategy for the construction of metal-organic open framework structures concerns the self-assembly of the appropriate metal salts and a tailored ligand in an appropriate solvent. However, nature tends to avoid a vacuum, and identical copies interpenetrate to fill the space. 3 The design and synthesis of new framework materials containing large pores is a continuous challenge. A new strategy for the construction of a microporous material is to use inorganic clusters as secondary building units in the assembly of the extended networks. 4 In this study, we tried to construct a new open framework structure using a large organic-inorganic hybrid secondary building unit that would prevent the interpenetration of identical copies.We have recently synthesized a nanometer-sized hexanuclear manganese metallamacrocycle using a chelating pentadentate ligand. 5 Each metal center in the hexanuclear manganese metallamacrocycle has been coordinated by five donor atoms from two chelating pentadentate ligands and an additional donor atom from a solvent molecule. Three solvent molecules coordinated at the metal centers are in one face of the cluster, and the other three solvent molecules coordinated at the other metal centers are in the other face of the cluster. In this study, we have tried to synthesize a new open framework material using a nanometersized rigid building block. We exchanged the coordinated solvent molecules of the metallamacrocycle using an exobidentate ligand to construct a three-dimensional framework.When an N-acetylsalicylhydrazidate (ashz 3-) was used as a pentadentate ligand for an octahedral manganese(III) ion and a 1,2-bis(4-pyridyl)ethane (bpea) was used as an exobidentate ligand, a self-assembled three-dimensional molecular open framework was easily constructed. 6 The hexanuclear manganese metallamacrocycle served as a discrete molecular building block, and the exobidentate ligand bpea connected the building block. A diagram of the open framework [Mn 6 (ashz) 6 (DMF) 2 (bpea) 2 ] n (1) is shown in Figure 1. 7 The building block, hexanuclear manganese metallamacrocycle [Mn 6 (ashz) 6 ], was similar to the previously reported hexanuclear manganese metallamacrocycle [Mn 6 (fshz) 6 (MeOH) 6 ]. 5 All building blocks were connected by exobidentate ligands, where the intermetal distance spaced by an exobidentate ligand was about 13.8 Å. The framework has four nanometer-sized channels along the crystallographic c axis per unit cell (Figures 1 and 2). Many solvent molecules were packed into the channels in the crystal structure. The framework was estimated to occupy only about 51% of the crystal volume by the PLATON program. 8 The average van der Waals diameter of the solvent channels w...

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