Dynamic DMF Binding in MOF-5 Enables the Formation of Metastable Cobalt-Substituted MOF-5 Analogues

[Image: see text] Multinuclear solid-state nuclear magnetic resonance, mass spectrometry, first-principles molecular dynamics simulations, and other complementary evidence reveal that the coordination environment around the Zn(2+) ions in MOF-5, one of the most iconic materials among metal–organic frameworks (MOFs), is not rigid. The Zn(2+) ions bind solvent molecules, thereby increasing their coordination number, and dynamically dissociate from the framework itself. On average, one ion in each cluster has at least one coordinated N,N-dimethylformamide (DMF) molecule, such that the formula of as-synthesized MOF-5 is defined as Zn(4)O(BDC)(3)(DMF)(x) (x = 1–2). Understanding the dynamic behavior of MOF-5 leads to a rational low-temperature cation exchange approach for the synthesis of metastable Zn(4–x)Co(x)O(terephthalate)(3) (x > 1) materials, which have not been accessible through typical high-temperature solvothermal routes thus far.