4 research outputs found
Carbon Dioxide Capture by a MetalâOrganic Framework with Nitrogen-Rich Channels Based on Rationally Designed Triazole-Functionalized Tetraacid Organic Linker
A semirigid tetraacid linker <b>H</b><sub><b>4</b></sub><b>L</b> functionalized with
1,2,3-triazole was rationally designed and synthesized to access nitrogen-rich
MOFs for selective adsorption of CO<sub>2</sub>. The cadmium MOF,
that is, <b>Cd-L</b>, obtained by the reaction of <b>H</b><sub><b>4</b></sub><b>L</b> with CdÂ(NO<sub>3</sub>)<sub>2</sub>, is found to be a 3D porous framework structure that is robust
to desolvation. Crystal structure analysis reveals channels that are
decorated by the triazole moieties of <b>L</b>. Gas adsorption
studies show that <b>Cd-L</b> MOF permits remarkable CO<sub>2</sub> uptake to the extent of 99 and 1000 cc/g at 1 and 30 bar,
respectively, at 0 °C. While literature survey reveals that <b>MIL-112</b>, constructed from a 1,2,3-triazole functionalized
linker, exhibits no porosity to gas adsorption due to structural flexibility,
the results with <b>Cd-L</b> MOF described herein emphasize how rigidification of the organic linker
improves gas uptake properties of the resultant MOF
Metal-Mediated Self-Assembly of a <i>Twisted</i> Biphenyl-Tetraacid Linker with Semi-rigid Core and Peripheral Flexibility: Concomitant Formation of Compositionally Distinct MOFs
A semi-rigid organic
linker, namely, 3,3â˛,5,5â˛-tetraÂkisÂ(4-(Îą-carboxy)ÂmethÂoxyÂphenyl)-2,2â˛,6,6â˛-tetraÂmethoxy-1,1â˛-biphenyl
(<b>H</b><sub><b>4</b></sub><b>L</b>), was designed
and synthesized to access metalâorganic frameworks (MOFs).
While the <i>ortho</i>-methoxy substituents in the biphenyl
core of <b>H</b><sub><b>4</b></sub><b>L</b> were
surmised to twist the aromatic planes and impart porosity to the resultant
MOFs, the (Îą-carÂboxy)ÂmethÂoxyÂphenyl moieties
at the periphery were envisaged to enable requisite flexibility for
metalâligand coordination polymerization. The reactions of <b>H</b><sub><b>4</b></sub><b>L</b> with Cd, Mn, and
Zn salts indeed yielded MOFs, i.e., <b>Cd-L</b>, <b>Mn-L</b>, <b>Zn-Lsqc</b>, and <b>Zn-Ldia</b>, with interesting
structural features and unusual inorganic SBUs. In particular, the
reaction of <b>H</b><sub><b>4</b></sub><b>L</b> with
ZnI<sub>2</sub> in DMF at 90 °C over 2 days led to concomitant
formation of a pair of <i>compositionally distinct</i> Zn-MOFs,
i.e., <b>Zn-Ldia</b> and <b>Zn-Lsqc</b>, each of which
could be accessed exclusively by controlling the reaction conditions.
The diversity observed in the structures of MOFs formed with the linker <b>H</b><sub><b>4</b></sub><b>L</b> with a limited number
of metal ions sufficiently emphasizes the importance of the attributes
of the linker in the formation of 3D MOFs; the latter are desirable
from the stability and exfoliation points of view when the MOFs are
explored for applications such as gas storage, catalysis, etc. In
corroboration of our previous results, it emerges that the flexibility
that is built into the structure of the organic linker, both at the
central core and at the periphery, leads to concomitant formation
of compositionally distinct MOFs in addition to diverse SBUs and disparate
framework topologies
Diverse MetalâOrganic Materials (MOMs) Based on 9,9â˛-Bianthryl-Dicarboxylic Acid Linker: Luminescence Properties and CO<sub>2</sub> Capture
A fluorescent
organic linker, namely, 10,10â˛-bisÂ(4-carboxyphenyl)-9,9â˛-bianthryl
(<b>H</b><sub><b>2</b></sub><b>L</b>), was rationally
designed and synthesized to access luminescent metalâorganic
materials (MOMs). A series of structurally diverse MOMs was synthesized
with the diacid linker <b>H</b><sub><b>2</b></sub><b>L</b> by reacting it with main group, transition, and lanthanide
metal ions under different conditions. Among them, <b>Zn-L</b> MOM is a 1D polymeric chain, while <b>Cd-L</b> is a 2D structure
in which 4,4â˛-bipyridyls mediate the formation of 2D networks
by linking up the 1D metalâcarboxylate chains. The <b>Pb-L</b> MOM is found to be a 2D polymeric net, while <b>Sr-L</b>,
obtained under similar reaction conditions, is a noninterpenetrated
3D polymeric structure; the extension from 2D to 3D framework occurs
by mediation of Cl<sup>â</sup> ions. Notably, the reaction
of <b>H</b><sub><b>2</b></sub><b>L</b> with the
lanthanide ions yielded isostructural 3D MOFs, i.e., <b>Tb-L</b>, <b>Eu-L</b>, <b>Sm-L</b>, <b>Nd-L</b>, <b>La-L</b>, <b>Pr-L</b>, <b>Gd-L</b>, and <b>Yb-L</b>, which are noninterpenetrated and porous. The Ln-MOFs are highly
robust and stable to solvent exclusion. The representative Ln-MOFS,
viz., <b>Tb-L</b>, <b>Eu-L</b>, and <b>Sm-L</b>,
are shown to exhibit gas adsorption at ambient temperatures; the CO<sub>2</sub> uptake capacities are found to be in the range of the highest
values observed for Ln-MOFs to date. All the MOMs, including lanthanide
MOFs, exhibit linker-based luminescence in the solid state
Tetraarylbiphenyl as a New Lattice Inclusion Host by Structure Reductionism: Shape and Size Complementarity Based on Torsional Flexibility
3,3â˛,5,5â˛-TetrakisÂ(2,6-dimethyl-4-methoxyphenyl)Âbiphenyl
(<b>TB</b>) was designed as a lattice inclusion host based on
a structure reductionistic approach. <b>TB</b> binds guests
in two different domains based on the premise that the two phenyl
rings of the biphenyl core remain coplanar in the solid state. The
versatility of <b>TB</b> as a host has been demonstrated by
its ability to include different guest molecules in the crystal lattice,
as revealed by X-ray crystal structure analyses. One observes preference
for guest location in the concave domain with the trough domain compromised.
The host <b>TB</b> is found to exploit torsional freedom about
the central Ď-bond between the two phenyl rings of the biphenyl
core to adopt discrete structures that are complementary in terms
of shape and size to include a given guest. In other words, <b>TB</b> behaves like a âmolecular chameleonâ that
undergoes structural adaptation in response to the guest via torsional
twist about the central Ď-bond. Quite remarkably, the inclusion
compounds with different guests having similar torsional angles between
the phenyl rings of the biphenyl core are found to be isostructural.
The torsion-induced structural morphosis in response to the guest
is found to completely offset binding in the trough region