Proton conductive materials become important for their utility to electrolytes of fuel cells or sensors. The proton conductivity of a one-dimensional coordination polymer, ferrous oxalate dihydrate, ...was evaluated and found to show 1.3 mS cm−1 at ambient temperature. The proton conductivity of this compound is extremely high at ambient temperature without any strong acidic group, and this result is suggestive of new proton conductive materials consisting of coordination polymers.
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The conversion of low-energy light into photons of higher energy based on sensitized triplet-triplet annihilation upconversion (TTA-UC) has emerged as a promising wavelength-shifting methodology ...because it permits UC at excitation powers as low as the solar irradiance. However, its application has been significantly hampered by the slow diffusion of excited molecules in solid matrices. Here, we introduce metal-organic frameworks (MOFs) that promote TTA-UC by taking advantage of triplet exciton migration among fluorophores that are regularly aligned with spatially controlled chromophore orientations. We synthesized anthracene-containing MOFs with different molecular orientations, and the analysis of TTA-UC emission kinetics unveiled a high triplet diffusion rate with a micrometre-scale diffusion length. Surface modification of MOF nanocrystals with donor molecules and their encapsulation in glassy poly(methyl methacrylate) (PMMA) allowed the construction of molecular-diffusion-free solid-state upconverters, which lead to an unprecedented maximization of overall UC quantum yield at excitation powers comparable to or well below the solar irradiance.
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IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, UL, UM, UPUK
Recent investigations into proton conduction in metal–organic frameworks (MOFs) indicate that MOFs are promising materials as a new class of proton conductors. Hydrated proton‐conductive MOFs show ...not only high proton conductivity of approximately 10−2 S cm−1, which is comparable to that of a practical organic polymer, but also structural visibility of proton‐conducting pathways inside the materials owing to their high crystallinity. Herein, studies on the design, synthesis, and proton‐conductive properties of MOFs with hydrated proton‐conductive systems are introduced.
Finding the way through: Metal–organic frameworks (MOFs) have emerged as a new class of proton conductors. Hydrated proton‐conductive MOFs show not only high proton conductivity, but also structural visibility of proton‐conducting pathways inside the materials owing to their high crystallinity (see figure). Studies on the design, synthesis, and proton‐conductive properties of MOFs with hydrated proton‐conductive systems are introduced.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Deep eutectic solvent (DES) was applied to the solvent of thermocell and high Seebeck coefficient (
S
e
) of the thermocell was achieved at high-temperatures operation. The
S
e
of a redox ...couple of ferricyanide and ferrocyanide (Fe(CN)
6
3−/4−
) reaches − 1.67 mV/K in a DES consisting of ethylene glycol and choline chloride. Spectroscopic analysis reveals that this is due to the strong interactions between the redox couple and the DES. Furthermore, the cell can operate over a wide temperature range of 135–165 °C. This result is a desired feature for waste-heat recovery applications.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We controlled the hydrophilicity of metal–organic frameworks (MOFs) to achieve high proton conductivity and high adsorption of water under low humidity conditions, by employing novel class of MOFs, ...{NR3(CH2COOH)}MCr(ox)3·nH2O (abbreviated as R-MCr, where R = Me (methyl), Et (ethyl), or Bu (n-butyl), and M = Mn or Fe): Me-FeCr, Et-MnCr, Bu-MnCr, and Bu-FeCr. The cationic components have a carboxyl group that functions as the proton carrier. The hydrophilicity of the cationic ions was tuned by the NR3 residue to decrease with increasing bulkiness of the residue: {NMe3(CH2COOH)}+ > {NEt3(CH2COOH)}+ > {NBu3(CH2COOH)}+. The proton conduction of the MOFs increased with increasing hydrophilicity of the cationic ions. The most hydrophilic sample, Me-FeCr, adsorbed a large number of water molecules and showed a high proton conductivity of ∼10–4 S cm–1, even at a low humidity of 65% relative humidity (RH), at ambient temperature. Notably, this is the highest conductivity among the previously reported proton-conducting MOFs that operate under low RH conditions.
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Ionic liquids (ILs) show promise as safe electrolytes for electrochemical devices. However, the conductivity of ILs decreases markedly at low temperatures because of strong interactions arising ...between the component ions. Metal-organic frameworks (MOFs) are appropriate microporous host materials that can control the dynamics of ILs
the nanosizing of ILs and tunable interactions of MOFs with the guest ILs. Here, for the first time, we report on the ionic conductivity of an IL incorporated within a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (Zn(MeIM)
, H(MeIM) = 2-methylimidazole) as the IL and the MOF, respectively. While the ionic conductivity of bulk EMI-TFSA showed a sharp decrease arising from freezing, the EMI-TFSA@ZIF-8 showed no marked decrease because there was no phase transition. The ionic conductivity of EMI-TFSA@ZIF-8 was higher than that of bulk EMI-TFSA below 250 K. This result points towards a novel method by which to design electrolytes for electrochemical devices such as batteries that can operate at low temperatures.
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Proton-conductive magnetic metal–organic frameworks (MOFs), {NR3(CH2COOH)}Ma IIMb III(ox)3 (abbreviated as R–M a M b : R = ethyl (Et), n-butyl (Bu); MaMb = MnCr, FeCr, FeFe) have been studied. The ...following six MOFs were prepared: Et–MnCr·2H2O, Et–FeCr·2H2O, Et–FeFe·2H2O, Bu–MnCr, Bu–FeCr, and Bu–FeFe. The structure of Bu–MnCr was determined by X-ray crystallography. Crystal data: trigonal, R3c (#161), a = 9.3928(13) Å, c = 51.0080(13) Å, Z = 6. The crystal consists of oxalate-bridged bimetallic layers interleaved by {NBu3(CH2COOH)}+ ions. Et–MnCr·2H2O and Bu–MnCr (R–MnCr MOFs) show a ferromagnetic ordering with T C of 5.5–5.9 K, and Et–FeCr·2H2O and Bu–FeCr (R–FeCr MOFs) also show a ferromagnetic ordering with T C of 11.0–11.5 K. Et–FeFe·2H2O and Bu–FeFe (R–FeFe MOFs) belong to the class II of mixed-valence compounds and show the magnetism characteristic of Néel N-type ferrimagnets. The Et-MOFs (Et–MnCr·2H2O, Et–FeCr·2H2O and Et–FeFe·2H2O) show high proton conduction, whereas the Bu–MOFs (Bu–MnCr, Bu–FeCr, and Bu–FeFe) show moderate proton conduction. Together with water adsorption isotherm studies, the significance of the carboxyl residues as proton carriers is revealed. The R–MnCr MOFs and the R–FeCr MOFs are rare examples of coexistent ferromagnetism and proton conduction, and the R–FeFe MOFs are the first examples of coexistent Néel N-type ferrimagnetism and proton conduction.
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The entropy change associated with proton‐coupled electron transfer (PCET) reactions significantly enhance the Seebeck coefficient (Se) of thermocells. A redox pair of Ru(Hxim)62+/3+ (Him=imidazole, ...x=0≈1) releases three protons in their one‐electron redox reactions in thermocells, which gave a remarkably high Se of −3.7 mV K−1 as confirmed by temperature‐dependent square wave voltammetry. The value of Se is proportional to the redox reaction entropy (ΔSrc), which increased with the number of dissociating protons. This result demonstrates the utility of PCET reaction toward efficient thermoelectric conversion.
Large redox entropy of proton‐coupled electron transfer reaction was utilized for thermoelectric energy conversion.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Here, we report an unprecedented chirality transfer from a metal–organic framework (MOF) to a polymer. In this work, unsubstituted polythiophene (PTh) was prepared in the nanochannels of a chiral ...MOF. Circular dichroism spectroscopy revealed that nanoconfinement of the polymer chains could endow optically inactive PTh with a chiral nature. The thickness of polymer chain assemblies could be controlled by tuning the loading amount of PTh, which resulted in a drastic change in the chiroptical properties. Note that PTh liberated from the host still exhibited chirality even without the chiral support. Remarkably, the recovered PTh presented high thermal stability of chirality up to 250 °C. Our findings show that the encapsulation of the polymer chains in chiral MOFs is a simple and effective methodology not only to express the chirality of polymers but also to elucidate the inter- and intrachain chirality in polymer assemblies.
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