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 Zn2(ATB)(H2O)·(H2O)3 (DMF)3 (MOF-33) are linked into diamond networks, while those of Ni2(ATC)(H2O)4· (H2O)4·(H2O)4 (MOF-34) have the structure of the Al network in SrAl2. Frameworks constructed from less symmetric tetrahedral SBUs have the Ga network of CaGa2O4 as illustrated by Zn2(ATC)·(C2H5OH)2 (H2O)2 (MOF-35) structure. Squares and tetrahedral SBUs in Zn2(MTB)(H2O)2·(DMF)6 (H2O)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 Zn2(NDC)3·[(HTEA)(DEF)(ClBz)]2 (MOF-37) form the most common structure for linking octahedral shapes, namely, the boron network in CaB6. New structure types for linking triangular and trigonal prismatic SBUs are found in Zn3O(BTC)2·(HTEA)2 (MOF-38) and Zn3O(HBTB)2(H2O)·(DMF)0.5 (H2O)3 (MOF-39). The synthesis, crystal structure, and structure analysis using the SBU approach are presented for each MOF.