Assembly of Metal−Organic Frameworks from Large Organic and Inorganic Secondary Building Units: New Examples and Simplifying Principles for Complex Structures

Abstract

The secondary building unit (SBU) has been identified as a useful tool in the analysis of complex metal−organic frameworks (MOFs). We illustrate its applicability to rationalizing MOF crystal structures by analysis of nine new MOFs which have been characterized by single-crystal X-ray diffraction. Tetrahedral SBUs in Zn(ADC)_2·(HTEA)_2 (MOF-31), Cd(ATC)·[Cd(H2O)_6](H2O)_5 (MOF-32), and Zn_2(ATB)(H_2O)·(H_2O)_3(DMF)_3 (MOF-33) are linked into diamond networks, while those of Ni_2(ATC)(H_2O)_4·(H_2O)_4 (MOF-34) have the structure of the Al network in SrAl_2. Frameworks constructed from less symmetric tetrahedral SBUs have the Ga network of CaGa_2O_4 as illustrated by Zn_2(ATC)·(C_2H_5OH)_2(H_2O)_2 (MOF-35) structure. Squares and tetrahedral SBUs in Zn_2(MTB)(H_2O)_2·(DMF)_6(H_2O)_5 (MOF-36) are linked into the PtS network, which is the simplest structure type known for the assembly of these shapes. The octahedral SBUs found in Zn_2(NDC)_3·[(HTEA)(DEF)(ClBz)]_2 (MOF-37) form the most common structure for linking octahedral shapes, namely, the boron network in CaB_6. New structure types for linking triangular and trigonal prismatic SBUs are found in Zn_3O(BTC)_2·(HTEA)_2 (MOF-38) and Zn_3O(HBTB)_2(H_2O)·(DMF)_(0.5)(H_2O)_3 (MOF-39). The synthesis, crystal structure, and structure analysis using the SBU approach are presented for each MOF.

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