Distinct Packings of Supramolecular Building Blocks in Metal–Organic Frameworks Based on Imidazoledicarboxylic Acid

When the supramolecular building block packings (face-centered, body-centered, and primitive cubic) with different interactions (hydrogen and coordination bonding) were controlled, four new structures based on octahedral M^II (M = Zn, Ni, Mn) and imidazoledicarboxylate were constructed. The interaction modes between the supramolecular building blocks affect the water stability of the structures. Furthermore, with uncoordinated carboxylate O atoms in the structures, these compounds demonstrate a strong capability of capturing metal ions in the solution

Ordered Vacancies and Their Chemistry in Metal–Organic Frameworks

Vacancies are common in solid materials, but it remains a challenge to introduce them at specific locations with controlled distributions. Here we report the creation of ordered metal vacancies and linker vacancies in a cubic metal–organic framework (MOF) based on Zn­(II) and pyrazolecarboxylic acid by removing a quarter of the metal ions and half of the linkers. The MOF with ordered vacancies shows increased pore size, thus allowing large dye molecules to fit in the pores. Furthermore, by filling the vacancies with new metals and new linkers, eight new single-crystalline MOFs with multicomponents in absolute order are introduced. The capability of performing stepwise elimination and addition reactions systematically in extended solids without destroying the structural integrity has generated complex MOF structures which otherwise cannot be made

Heterogeneity within a Mesoporous Metal–Organic Framework with Three Distinct Metal-Containing Building Units

Materials built from multiple constituents have revealed emerging properties that are beyond linear integration of those from single components. We report a mesoporous metal–organic framework made from three geometrically distinct metal-containing secondary building units (SBUs) as a result of topological induction. The combinations of the Cu-based triangular, Zn-based octahedral, and Zn-based square pyramidal SBUs have created four types of cages in the network, despite that only one organic linker pyrazolecarboxylate was used. The longest distance for molecules maneuvering inside the largest cage is 5.2 nm. Furthermore, the complex and diversified pore environments allow the installation of various new functionalities in the framework as well as the expedited Ag nanoparticle formation in the pores. As presented in the molecule movement diagram, the crystal has provided specific arrangements of cages and apertures with distinct chemical features for guests transporting between the pores

Structure Transformation of a Luminescent Pillared-Layer Metal–Organic Framework Caused by Point Defects Accumulation

Pillared-layer metal–organic frameworks (MOFs) are often encountered to “collapse” upon external stimuli due to weak interactions between the layers and the pillars. However, the detailed local structural change, especially the accumulation of defects due to intricately disordered bond dissociations, is not clear due to the complicated and dynamic nature of the collapse. We report a luminescent pillared-layer MOF structure, FDM-22, using zinc dicarboxylates as layers and dipyridyl ligands as pillars, in which three different transformed structures were captured along the increasing number of coordination bond dissociations between zinc metals and pyridine linkers. The transformation is triggered by these local point defect formations in the MOF, which further contribute to the modulation of its luminescence property, as well as prominent change in the morphology and pore distribution of the MOF. Evidenced by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), each of the pillar ligands has only one pyridyl group coordinated to a Zn­(II) ion eventually, with the other uncoordinated pyridyl group pointing to the pore. With ∼10% of the coordination bonds breaking within the framework, FDM-22 provides a high concentration of active metal sites in the framework

Structure Transformation of a Luminescent Pillared-Layer Metal–Organic Framework Caused by Point Defects Accumulation

Pillared-layer metal–organic frameworks (MOFs) are often encountered to “collapse” upon external stimuli due to weak interactions between the layers and the pillars. However, the detailed local structural change, especially the accumulation of defects due to intricately disordered bond dissociations, is not clear due to the complicated and dynamic nature of the collapse. We report a luminescent pillared-layer MOF structure, FDM-22, using zinc dicarboxylates as layers and dipyridyl ligands as pillars, in which three different transformed structures were captured along the increasing number of coordination bond dissociations between zinc metals and pyridine linkers. The transformation is triggered by these local point defect formations in the MOF, which further contribute to the modulation of its luminescence property, as well as prominent change in the morphology and pore distribution of the MOF. Evidenced by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), each of the pillar ligands has only one pyridyl group coordinated to a Zn­(II) ion eventually, with the other uncoordinated pyridyl group pointing to the pore. With ∼10% of the coordination bonds breaking within the framework, FDM-22 provides a high concentration of active metal sites in the framework

Reversible Redox Activity in Multicomponent Metal–Organic Frameworks Constructed from Trinuclear Copper Pyrazolate Building Blocks

Inorganic functionalization of metal–organic frameworks (MOFs), such as incorporation of multiple inorganic building blocks with distinct metals into one structure and further modulation of the metal charges, endows the porous materials with significant properties toward their applications in catalysis. In this work, by an exploration of the role of 4-pyrazolecarboxylic acid (H₂PyC) in the formation of trinuclear copper pyrazolate as a metalloligand in situ, four new MOFs with multiple components in order were constructed through one-pot synthesis. This metalloligand strategy provides multicomponent MOFs with new topologies (<b>tub</b> for FDM-4 and <b>tap</b> for FDM-5) and is also compatible with a second organic linker for cooperative construction of complex MOFs (1,4-benzenedicarboxylic acid for FDM-6 and 2,6-naphthalenedicarboxylic acid for FDM-7). The component multiplicity of these MOFs originates from PyC’s ability to separate Cu and Zn on the basis of their differentiated binding affinities toward pyrazolate and carboxylate. These MOFs feature reversible and facile redox transformations between Cu^I₃(PyC)₃ and Cu^II₃(μ-OH)­(PyC)₃(OH)₃ without altering the connecting geometries of the units, thus further contributing to the significant catalytic activities in the oxidation of CO and aromatic alcohols and the decomposition of H₂O₂. This study on programming multiple inorganic components into one framework and modulating their electronic structures is an example of functionalizing the inorganic units of MOFs with a high degree of control