3 research outputs found
Nanostructuration of PEDOT in Porous Coordination Polymers for Tunable Porosity and Conductivity
A series of conductive porous composites
were obtained by the polymerization
of 3,4-ethylenedioxythiophene (EDOT) in the cavities of MIL–101Â(Cr).
By controlling the amount of EDOT loaded into the host framework,
it was possible to modulate the conductivity as well as the porosity
of the composite. This approach yields materials with a reasonable
electronic conductivity (1.1 × 10<sup>−3</sup> S·cm<sup>–1</sup>) while maintaining high porosity (<i>S</i><sub>BET</sub> = 803 m<sup>2</sup>/g). This serves as a promising
strategy for obtaining highly nanotextured conductive polymers with
very high accessibility for small gas molecules, which are beneficial
to the fabrication of a chemiresistive sensor for the detection of
NO<sub>2</sub>
Confinement of Single Polysilane Chains in Coordination Nanospaces
Understanding
the intrinsic properties of single conducting polymer chains is of
interest, largely for their applications in molecular devices. In
this study, we report the accommodation of single polysilane chains
with hole-transporting ability in porous coordination polymers (PCPs),
[AlÂ(OH)Â(L)]<sub><i>n</i></sub> (<b>1a</b>; L = 2,6-naphthalenedicarboxylate,
channel size = 8.5 × 8.5 Å<sup>2</sup>, <b>1b</b>;
L = 4,4′-biphenyldicarboxylate, channel size = 11.1 ×
11.1 Ã…<sup>2</sup>). Interestingly, the isolation of single polysilane
chains increased the values of carrier mobility in comparison with
that in the bulk state due to the elimination of the slow interchain
hole hopping. Moreover, even when the chains are isolated one another,
the main chain conformation of polysilane could be controlled by changing
the pore environment of PCPs, as evidenced by Raman spectroscopy,
solid-state NMR measurements, and molecular dynamics simulation. Hence,
we succeeded in varying the conducting property of single polysilane
chains. Additionally, polysilanes have a drawback, photodegradation
under ultraviolet light, which should be overcome for the application
of polysilanes. It is noteworthy that the accommodation of polysilane
in the nanopores did not exhibit photodegradation. These results highlight
that PCP–polysilane hybrids are promising candidates for further
use in the field of molecular electronics
Lanthanide-Based Porous Coordination Polymers: Syntheses, Slow Relaxation of Magnetization, and Magnetocaloric Effect
Two lanthanide-containing structurally
analogous porous coordination polymers (PCPs) have been isolated with
the general molecular formula [Ln<sub>2</sub>(L<sub>1</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>(ox)]<sub><i>n</i></sub>.4<i>n</i>H<sub>2</sub>O (where L<sub>1</sub> = fumarate, ox = oxalate;
Ln = Dy (<b>1</b>), Gd (<b>2</b>)). Thermogravimetric
analysis (TGA) and TG-MS measurements performed on <b>1</b> and <b>2</b> suggest that not only the solvated water molecules in the
crystal lattice but also the four coordinated water molecules on the
respective lanthanides in <b>1</b> and <b>2</b> are removed
upon activation. Due to the removal of the waters, <b>1</b> and <b>2</b> lost their crystallinity and became amorphous, as confirmed
by powder X-ray diffraction (PXRD). We propose the molecular formula
[Ln<sub>2</sub>(L<sub>1</sub>)<sub>2</sub>(ox)]<sub><i>n</i></sub> for the amorphous phase of <b>1</b> and <b>2</b> (where Ln = Dy (<b>1′</b>), Gd (<b>2′</b>)) on the basis of XANES, EXAFS, and other experimental investigations.
Magnetization relaxation dynamics probed on <b>1</b> and <b>1′</b> reveal two different relaxation processes with effective
energy barriers of 53.5 and 7.0 cm<sup>–1</sup> for <b>1</b> and 45.1 and 6.4 cm<sup>–1</sup> for <b>1′</b>, which have been rationalized by detailed ab initio calculations.
For the isotropic lanthanide complexes <b>2</b> and <b>2′</b>, magnetocaloric effect (MCE) efficiency was estimated through detailed
magnetization measurements. We have estimated −Δ<i>S</i><sub><i>m</i></sub> values of 52.48 and 41.62
J kg<sup>1–</sup> K<sup>–1</sup> for <b>2′</b> and <b>2</b>, respectively, which are one of the largest values
reported for an extended structure. In addition, a 26% increase in
−Δ<i>S</i><sub>m</sub> value in <b>2′</b> in comparison to <b>2</b> is achieved by simply removing the
passively contributing (for MCE) solvated water molecule in the lattice
and coordinated water molecules