7 research outputs found

    Deciphering the Spatial Arrangement of Metals and Correlation to Reactivity in Multivariate Metal–Organic Frameworks

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    Thirty-six porphyrin-based metal–organic frameworks (MOFs) with composition of <b>(M</b><sub><b>3</b></sub><b>O)</b><sub><b>2</b></sub><b>(TCPP-M)</b><sub><b>3</b></sub> and M<sub>3</sub>O trigonal SBUs of various metals, Mg<sub>3</sub>O, Mn<sub>3</sub>O, Co<sub>3</sub>O, Ni<sub>3</sub>O, and Fe<sub>3</sub>O including mixed-metal SBUs, Mn<sub><i>x</i></sub>Fe<sub>3–<i>x</i></sub>O, Ni<sub><i>x</i></sub>Fe<sub>3–<i>x</i></sub>O, Co<sub><i>x</i></sub>Ni<sub>3–<i>x</i></sub>O, Mn<sub><i>x</i></sub>Co<sub>3–<i>x</i></sub>O, Mn<sub><i>x</i></sub>Mg<sub>3–<i>x</i></sub>O, and Mn<sub><i>x</i></sub>Ni<sub>3–<i>x</i></sub>O were synthesized and characterized. These multivariate MOFs (MTV-MOFs) were examined by X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, and for the first time, their metal spatial arrangement deciphered and were found to exist in the form of either domains or well-mixed. We find that MTV-MOFs with well-mixed metals in their SBUs, rather than the SBUs having one kind of metal but different from one SBU to another, perform better than the sum of their parts in the test reaction involving the photo-oxidation of 1,5-dihydroxynaphthalene

    Multivariate Metal–Organic Frameworks for Dialing-in the Binding and Programming the Release of Drug Molecules

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    We report the control of guest release profiles by dialing-in desirable interactions between guest molecules and pores in metal–organic frameworks (MOFs). The interactions can be derived by the rate constants that were quantitatively correlated with the type of functional group and its proportion in the porous structure; thus the release of guest molecules can be predicted and programmed. Specifically, three probe molecules (ibuprofen, rhodamine B, and doxorubicin) were studied in a series of robust and mesoporous MOFs with multiple functional groups [MIL-101­(Fe)-(NH<sub>2</sub>)<sub><i>x</i></sub>, MIL-101­(Fe)-(C<sub>4</sub>H<sub>4</sub>)<sub><i>x</i></sub>, and MIL-101­(Fe)-(C<sub>4</sub>H<sub>4</sub>)<sub><i>x</i></sub>(NH<sub>2</sub>)<sub>1–<i>x</i></sub>]. The release rate can be adjusted by 32-fold [rhodamine from MIL-101­(Fe)-(NH<sub>2</sub>)<sub><i>x</i></sub>], and the time of release peak can be shifted by up to 12 days over a 40-day release period [doxorubicin from MIL-101­(Fe)-(C<sub>4</sub>H<sub>4</sub>)<sub><i>x</i></sub>(NH<sub>2</sub>)<sub>1–<i>x</i></sub>], which was not obtained in the physical mixture of the single component MOF counterparts nor in other porous materials. The corelease of two pro-drug molecules (ibuprofen and doxorubicin) was also achieved

    Precise Distance Control and Functionality Adjustment of Frustrated Lewis Pairs in Metal–Organic Frameworks

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    We report the construction of frustrated Lewis pairs (FLPs) in a metal–organic framework (MOF), where both Lewis acid (LA) and Lewis base (LB) are fixed to the backbone. The anchoring of a tritopic organoboron linker as LA and a monotopic linker as LB to separate metal oxide clusters in a tetrahedron geometry allows for the precise control of distance between them. As the type of monotopic LB linker varies, pyridine, phenol, aniline, and benzyl alcohol, a series of 11 FLPs were constructed to give fixed distances of 7.1, 5.5, 5.4, and 4.8 Å, respectively, revealed by 11B–1H solid-state nuclear magnetic resonance spectroscopy. Keeping LA and LB apart by a fixed distance makes it possible to investigate the electrostatic effect by changing the functional groups in the monotopic LB linker, while the LA counterpart remains unaffected. This approach offers new chemical environments of the active site for FLP-induced catalysis

    Synthesis and Characterization of Metal–Organic Framework-74 Containing 2, 4, 6, 8, and 10 Different Metals

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    Metal–organic frameworks (MOFs) containing more than two kinds of metal ions mixed in one secondary building unit are rare because the synthesis often yields mixed MOF phases rather than a pure phase of a mixed-metal MOF (MM-MOF). In this study, we use a one-pot reaction to make microcrystalline MOF-74 [M<sub>2</sub>(DOT); DOT = dioxidoterephthalate] with 2 (Mg and Co), 4 (Mg, Co, Ni, and Zn), 6 (Mg, Sr, Mn, Co, Ni, and Zn), 8 (Mg, Ca, Sr, Mn, Fe, Co, Ni, and Zn), and 10 (Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Zn, and Cd) different kinds of divalent metals. The powder X-ray diffraction patterns of MM-MOF-74 were identical with those of single-metal MOF-74, and no amorphous phases were found by scanning electron microscopy. The successful preparation of guest-free MM-MOF-74 samples was confirmed by N<sub>2</sub> adsorption measurements. Elemental analysis data also support the fact that all metal ions used in the MOF synthesis are incorporated within the same MOF-74 structure. Energy-dispersive X-ray spectroscopies indicate that metal ions are heterogeneously distributed within each of the crystalline particles. This approach is also employed to incorporate metal ions (i.e., Ca, Sr, Ba, and Cd) from which the parent MOF structure could not be made as a single-metal-containing MOF

    Introduction of Functionality, Selection of Topology, and Enhancement of Gas Adsorption in Multivariate Metal–Organic Framework-177

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    Metal–organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral Zn<sub>4</sub>O­(−COO)<sub>6</sub> and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the <b>qom</b> topology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks. In the case of octahedron and triangle combinations, MOFs based on pyrite (<b>pyr</b>) and rutile (<b>rtl</b>) nets were expected instead of <b>qom</b>. In this study, we have made 24 MOF-177 structures with different functional groups on the triangular BTB linker, having one or more functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (<b>qom</b>, <b>pyr</b>, and <b>rtl</b>), and that mixing of functionalities (-H, -NH<sub>2</sub>, and -C<sub>4</sub>H<sub>4</sub>) is an important strategy for the incorporation of a specific functionality (-NO<sub>2</sub>) into MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-177 structures leads to enhancement of hydrogen uptake by 25%

    Introduction of Functionality, Selection of Topology, and Enhancement of Gas Adsorption in Multivariate Metal–Organic Framework-177

    No full text
    Metal–organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral Zn<sub>4</sub>O­(−COO)<sub>6</sub> and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the <b>qom</b> topology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks. In the case of octahedron and triangle combinations, MOFs based on pyrite (<b>pyr</b>) and rutile (<b>rtl</b>) nets were expected instead of <b>qom</b>. In this study, we have made 24 MOF-177 structures with different functional groups on the triangular BTB linker, having one or more functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (<b>qom</b>, <b>pyr</b>, and <b>rtl</b>), and that mixing of functionalities (-H, -NH<sub>2</sub>, and -C<sub>4</sub>H<sub>4</sub>) is an important strategy for the incorporation of a specific functionality (-NO<sub>2</sub>) into MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-177 structures leads to enhancement of hydrogen uptake by 25%
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