7 research outputs found
Deciphering the Spatial Arrangement of Metals and Correlation to Reactivity in Multivariate MetalâOrganic Frameworks
Thirty-six
porphyrin-based metalâorganic 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>3â<i>x</i></sub>O, Ni<sub><i>x</i></sub>Fe<sub>3â<i>x</i></sub>O, Co<sub><i>x</i></sub>Ni<sub>3â<i>x</i></sub>O, Mn<sub><i>x</i></sub>Co<sub>3â<i>x</i></sub>O, Mn<sub><i>x</i></sub>Mg<sub>3â<i>x</i></sub>O, and Mn<sub><i>x</i></sub>Ni<sub>3â<i>x</i></sub>O were synthesized
and characterized. These multivariate MOFs (MTV-MOFs) were examined
by X-ray photoelectron spectroscopy, UVâvis 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 MetalâOrganic Frameworks for Dialing-in the Binding and Programming the Release of Drug Molecules
We report the control
of guest release profiles by dialing-in desirable
interactions between guest molecules and pores in metalâorganic
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-101Â(Fe)-(NH<sub>2</sub>)<sub><i>x</i></sub>, MIL-101Â(Fe)-(C<sub>4</sub>H<sub>4</sub>)<sub><i>x</i></sub>, and MIL-101Â(Fe)-(C<sub>4</sub>H<sub>4</sub>)<sub><i>x</i></sub>(NH<sub>2</sub>)<sub>1â<i>x</i></sub>]. The release rate can be
adjusted by 32-fold [rhodamine from MIL-101Â(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-101Â(Fe)-(C<sub>4</sub>H<sub>4</sub>)<sub><i>x</i></sub>(NH<sub>2</sub>)<sub>1â<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 MetalâOrganic Frameworks
We
report the construction of frustrated Lewis pairs (FLPs) in
a metalâorganic 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 Ă
, respectively, revealed by 11Bâ1H 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 MetalâOrganic Framework-74 Containing 2, 4, 6, 8, and 10 Different Metals
Metalâorganic
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 MetalâOrganic Framework-177
Metalâorganic framework-177
(MOF-177) is one of the most
porous materials whose structure is composed of octahedral Zn<sub>4</sub>OÂ(âCOO)<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 MetalâOrganic Framework-177
Metalâorganic framework-177
(MOF-177) is one of the most
porous materials whose structure is composed of octahedral Zn<sub>4</sub>OÂ(âCOO)<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%