Ken-Ichi Otake

Increased Electrical Conductivity in a Mesoporous Metal–Organic Framework Featuring Metallacarboranes Guests

Nickel(IV) bis(dicarbollide) is incorporated in a zirconium-based metal-organic framework (MOF), NU-1000, to create an electrically conductive MOF with mesoporosity. All the nickel bis(dicarbollide) units are located as guest molecules in the microporous channels of NU-1000, which permits the further incorporation of other active species in the remaining mesopores. For demonstration, manganese oxide is installed on the nodes of the electrically conductive MOF. The electrochemically addressable fraction and specific capacitance of the manganese oxide in the conductive framework are more than 10 times higher than those of the manganese oxide in the parent MOF.

Single-Atom-Based Vanadium Oxide Catalysts Supported on Metal–Organic Frameworks: Selective Alcohol Oxidation and Structure–Activity Relationship

We report the syntheses, structures, and oxidation catalytic activities of a single-atom-based vanadium oxide incorporated in two highly crystalline MOFs, Hf-MOF-808 and Zr-NU-1000. These vanadium catalysts were introduced by a postsynthetic metalation, and the resulting materials (Hf-MOF-808-V and Zr-NU-1000-V) were thoroughly characterized through a combination of analytic and spectroscopic techniques including single-crystal X-ray crystallography. Their catalytic properties were investigated using the oxidation of 4-methoxybenzyl alcohol under an oxygen atmosphere as a model reaction. Crystallographic and variable-temperature spectroscopic studies revealed that the incorporated vanadium in Hf-MOF-808-V changes position with heat, which led to improved catalytic activity.

Revisiting the structural homogeneity of NU-1000, a Zr-based metal–organic framework

Synthesis and activation of phase-pure and defect-free metal–organic frameworks (MOFs) are essential for establishing accurate structure–property relationships. Primarily suffering from missing linker and/or node defects, Zr6-based MOFs can have polymorphs, structures with the identical linker and node but different connectivity, which can create multiple phases in a sample that complicate the characterization. Here, we report the synthesis of phase-pure NU-1000, a mesoporous Zr6-based MOF that typically contains a significant secondary phase within the individual crystallites. Large biomolecules and smaller inorganic molecules have been installed in NU-1000 as probes to verify the near elimination of the microporous secondary-phase. Obtaining structurally homogenous MOFs will assist the design of new materials with distinct structural features.

CCDC 1852111: Experimental Crystal Structure Determination

Related Article: Yuanyuan Zhang, Xuan Zhang, Jiafei Lyu, Ken-ichi Otake, Xingjie Wang, Louis R. Redfern, Christos D. Malliakas, Zhanyong Li, Timur Islamoglu, Bo Wang, Omar K. Farha|2018|J.Am.Chem.Soc.|140|11179|doi:10.1021/jacs.8b06789

CCDC 1850693: Experimental Crystal Structure Determination

Related Article: Yuanyuan Zhang, Xuan Zhang, Jiafei Lyu, Ken-ichi Otake, Xingjie Wang, Louis R. Redfern, Christos D. Malliakas, Zhanyong Li, Timur Islamoglu, Bo Wang, Omar K. Farha|2018|J.Am.Chem.Soc.|140|11179|doi:10.1021/jacs.8b06789

CCDC 1850691: Experimental Crystal Structure Determination

Related Article: Yuanyuan Zhang, Xuan Zhang, Jiafei Lyu, Ken-ichi Otake, Xingjie Wang, Louis R. Redfern, Christos D. Malliakas, Zhanyong Li, Timur Islamoglu, Bo Wang, Omar K. Farha|2018|J.Am.Chem.Soc.|140|11179|doi:10.1021/jacs.8b06789

CCDC 1852113: Experimental Crystal Structure Determination

Related Article: Yuanyuan Zhang, Xuan Zhang, Jiafei Lyu, Ken-ichi Otake, Xingjie Wang, Louis R. Redfern, Christos D. Malliakas, Zhanyong Li, Timur Islamoglu, Bo Wang, Omar K. Farha|2018|J.Am.Chem.Soc.|140|11179|doi:10.1021/jacs.8b06789

CCDC 1852112: Experimental Crystal Structure Determination

Related Article: Yuanyuan Zhang, Xuan Zhang, Jiafei Lyu, Ken-ichi Otake, Xingjie Wang, Louis R. Redfern, Christos D. Malliakas, Zhanyong Li, Timur Islamoglu, Bo Wang, Omar K. Farha|2018|J.Am.Chem.Soc.|140|11179|doi:10.1021/jacs.8b06789

A Flexible Metal-Organic Framework with 4-Connected Zr6 Nodes

Zr-based metal-organic frameworks (MOFs) have been known for their excellent stability; however, due to the high connectivity of the Zr6 nodes, it is challenging to introduce flexibility into Zr-MOFs. Here we present a flexible Zr-MOF named NU-1400 comprising 4-connected Zr6 nodes and tetratopic linkers. It exhibits guest-dependent structural flexibility with up to 48% contraction in the unit cell volume as evidenced by single-crystal X-ray diffraction studies. The expanded or contracted conformations of NU-1400 showed drastically different reactivity toward the hydrolysis of a nerve agent simulant owing to the size-selective effect toward the reactant.

Beyond the Active Site: Tuning the Activity and Selectivity of a Metal–Organic Framework-Supported Ni Catalyst for Ethylene Dimerization

To modify its steric and electronic properties as a support for heterogeneous catalysts, electron-withdrawing and electron-donating ligands, hexafluoroacetylacetonate (Facac-) and acetylacetonate (Acac-), were introduced to the metal-organic framework (MOF), NU-1000, via a process akin to atomic layer deposition (ALD). In the absence of Facac- or Acac-, NU-1000-supported, AIM-installed Ni(II) sites yield a mixture of C4, C6, C8, and polymeric products in ethylene oligomerization. (AIM = ALD-like deposition in MOFs). In contrast, both Ni-Facac-AIM-NU-1000 and Ni-Acac-AIM-NU-1000 exhibit quantitative catalytic selectivity for C4 species. Experimental findings are supported by density functional theory calculations, which show increases in the activation barrier for the C-C coupling step, due mainly to rearrangement of the siting of Facac- or Acac- to partially ligate added nickel. The results illustrate the important role of structure-tuning support modifiers in controlling the activity of MOF-sited heterogeneous catalysts and in engendering catalytic selectivity. The results also illustrate the ease with which crystallographically well-defined modifications of the catalyst support can be introduced when the node-coordinating molecular modifier is delivered via the vapor phase.