Anhydrous Conditions Research Articles

Heterometallic [Ln(hfac)3Cu(acac)2] complexes with late 4f ions

Heterometallic [Ln(hfac)3Cu(acac)2] complexes (Ln = Eu 1, Dy 2, Er 3) can be prepared along the f-transition series. X-rays diffraction studies on well-shaped single crystals revealed for 1 – 3 a dinuclear structure. No ligand scrambling occurred, a Lewis acid-base interaction has been observed with the two metals bridged through two oxygen atoms of the acetylacetonato ligands and an oxygen atom of a hexafluoroacetylacetonato ligand. Compounds 2 and 3 can be obtained only in anhydrous conditions. (1) can be sublimed under reduced pressure, and crystals of the sublimed product, 1a, showed a polymorph structure with the same molecular identity. Magnetic studies have been carried out on 2, displaying an antiferromagnetic interaction and a field-induced slow relaxing magnetic moment with a significant phonon bottleneck effect. Compound 3, on the other hand, did not present any magnetization dynamics, with or without applied field. Quantum mechanical calculations rationalize the variation of the bond strengths from the reagents to the heterometallic complexes and quantify the Ln and Cu direct interaction, which is relevant, especially for 2.

Modulation of defects in metal organic gels to enhance anhydrous proton conduction from subzero to moderate temperature

Exploitation of solid-state proton-conducting materials with high anhydrous proton conductivity from subzero temperature (<273 K) to moderate temperature (>353 K) is a great challenge. Here, Brönsted acid-dopped zirconium-organic xerogels (Zr/BTC-xerogels) are prepared for anhydrous proton conduction from subzero to moderate temperature. Abundant acid sites and strong H-bonding interactions make the CF3SO3H (TMSA)-introduced xerogel gain high proton conductivity from 9.0 × 10-4 S cm−1 (253 K) to 1.40 × 10-2 S cm−1 (363 K) under anhydrous conditions, which are in the leading level. This provides a new possibility to develop wide-operating-temperature conductors.

A Green Approach to the Synthesis of Fused Benzo[1,8]-naphthyridine derivatives by One-pot Three Component Reaction

One pot synthesis of 3,3-dimethyl-3,4-dihydro-2Hdibenzo [b,g][1,8]-naphthyridin-1-one derivatives has been accomplished by three component protocol involving 2-chloroquinoline-3-carbaldehydes, cyclichexanedione and ammonium acetate as a base catalyst. Mild reaction conditions and good yields are obtained by reaction lying in green approach. This route avoids the use of toxic organic solvents, expensive catalysts and anhydrous conditions. The protocol used narrates the interesting development of highly selective methods for the contruction of Ncontaining heterocycle moiety in aqueous medium reaction.

Corrosion properties of sodium carboxymethyl cellulose on metal surface base on molecular dynamics simulation

Sodium carboxymethyl cellulose (SCMC) is an effective corrosion inhibitor that provides good protection to metal surfaces. This study investigates the corrosion inhibition properties of SCMC on Fe, Cu, and Al using molecular dynamics simulations. The effects of the adsorption configuration, interaction energy of SCMC on different metal surfaces, and the degree of polymerization change of SCMC molecules were analyzed. The results show that under anhydrous conditions, the adsorption energy between the SCMC and the metal surface increases with its degree of polymerization. The SCMC also gets close to the different metal surfaces, and the carboxyl oxygen atoms in the molecular chain of SCMC are mainly distributed at a distance of about 2.9 Å from the metal surface. It illustrates a strong interaction between SCMC and metal surfaces, and the SCMC breaks free from the water molecules and eventually still adsorbs to the metal surface in water environment, but the adsorption energy is reduced by the water environment.

Finely Adjusted Intrinsically Microporous Copolyimide Electrolyte Membranes for Fuel Cells Operating in a Wide Temperature Range

The development of proton exchange membrane fuel cells (PEMFCs) that operate over a wide temperature range without additional humidification systems remains challenging. In this work, wide-temperature-range proton exchange membranes (PEMs) were constructed from novel Tröger’s base (TB)-based intrinsically microporous copolyimides (co-PIs) finely adjusted by incorporating crown ether units into chain backbones. Owing to the strong siphoning effect of existing microporosity and hydrogen bonds or the acid–base interactions of crown ether and TB units with phosphoric acid (PA) and/or H2O, the PA-doped co-PI membrane electrode assemblies (MEAs) can easily operate stably from 30 to 160 °C under H2/air conditions even without any external humidifiers. Regarding its single-cell performance, PI-TB-N30C achieved maximum power densities of 250 and 361 mW cm–2 at 80 and 160 °C, respectively, under anhydrous conditions. In addition, PA-doped co-PI MEA can accomplish long-term stable operation under low or high temperatures for 120 h. The structural architectures for PEMs based on finely adjusted microporous co-PIs extend beyond the current capabilities of existing PEMFCs.

A direct alkylation of resorcinols

Alkylation of resorcinol and methyl-substituted resorcinols and its methyl ethers with alkyl bromides in water and anhydrous organic solvents led to mono- and/or dialkylated resorcinols and alkyl cyclohexendiones, depending on the structure of the starting substrates and reaction conditions. Selective di-alkylation was achieved in both, aqueous and anhydrous conditions, up to 76% yield. Resorcinol monomethyl ethers behaved similarly to phenols, giving in dry organic solvents predominantly ortho -substituted products, and a mixture of ortho- and para-substituted products together with resorcinol ethers in aqueous solution. The alkylation of 2,4,6-trimethyl resorcinol monomethyl ether showed selective 2 C-alkylation in 53% yield. 2-Methyl resorcinol with electrophiles in excess afforded in tetra-alkylation up to 72% yield.

Protic ion-crosslinked polymer ionic liquid (PIL) based on linear oligomers

A method for the synthesis of a protic ion-crosslinked polymeric ionic liquid (PIL) which turns into a liquid state at a temperature below 50 °C using a reaction of basic and acidic linear oligomers was developed. The product of interaction of α,ω-diglycidyl ester of oligoethylene oxide MM 1000 with an excess of 1-(3-aminopropyl)imidazole (PEO–2Im) was used as the basic oligomer. It contains two types of basic centers with a significant difference in basicity (aliphatic secondary amino groups and imidazole heterocycles), as well as secondary hydroxyl groups at the ends of oligoether chain. A linear oligomer with terminal sulfonic acid groups (PEO–2SO3H) was obtained by the interaction of of oligoethylene oxide MM 1000 with 2-sulfobenzoic acid cyclic anhydride. Protic ion-crosslinked PIL was synthesized by completely neutralization of basic centers of oligomer PEO–2Im by acidic oligomer PEO–2SO3H at their molar ratio 1:2 respectively. The structure of the obtained PIL was characterized by FTIR and 1Н NMR- spectroscopy methods. According to DSC, the synthesized ion-crosslinked PIL contains two types of crystalline formations with melting temperatures of 36,3 °C and 45,8 °C formed by fragments of oligoethylene oxide during the transfer of protons between different types of ion centers. Determined by the TGA method the temperature of the onset of decomposition, which corresponds to 5% mass loss, is 265 °C. The proton conductivity of the ion-crosslinked PIL was studied by the DRS method in anhydrous conditions in the temperature range from 40 to 100 °C. At a temperature of 100 °C, the proton conductivity is 3,1·10-4 S/cm. The achieved values of proton conductivity and thermal stability make the obtained compound promising as a proton-conducting medium for various electrochemical devices.

Theoretical Calculations of Organic Salts and Their Correlation with Proton Conductivity

In the field of high-temperature polymer electrolyte membrane fuel cells, the concern over the proton conductor possible to apply to the high-temperature anhydrous condition has risen. Thus, poly(4-vinylpyridine)s were employed as not only an organic donor polymer with pyridine rings as the base but also heat-resistant materials. We introduced various acids as the acceptors into the polymer side chain through the acid–base reaction to form poly(4-vinylpyridinium salt)s (PVPySAs). The verification that the substituent design as the model in the polymer side chain of PVPySAs by the density functional theory was carried out to discuss what influences their high or low proton conductions. The results indicated that the shortened protonated atomic distance between acid and base moieties enhanced the conductivity of the organic salts. In addition, the pKa and number of protons of the used acid groups give an effect on the proton conductivity.

Crosslinked poly (isatin biphenyl spirofluorene) membranes for proton conduction over a wide temperature range from −40 to 160 °C

It is desired to develop proton exchange membranes (PEMs) working in a wide temperature range considering the practical working condition of devices using the PEMs as the electrolyte. Herein, a novel polymer of poly (isatin biphenyl spirofluorene) (PIBS) is first synthesized and it is afterwards crosslinked by 1,3-bis(4-piperidyl) propane (P) to fabricate membranes. The membranes can work in a temperature range of −40 to 160 °C after doping with phosphoric acid (PA). The proton conductivity of the PA doped membrane reaches 4.4 × 10−3 S cm−1 at −40 °C under 80% relative humidity (RH) and 0.16 S cm−1 at 160 °C without humidifying. We demonstrate the uses of the prepared PA doped PIBS-P membranes as membrane electrolytes in single fuel cells within 100–160 °C under anhydrous condition, and in water electrolytic cells within −20 to 60 °C, respectively.

Anhydrous Superprotonic Conductivity in the Zirconium Acid Triphosphate ZrH5 (PO4 )3.

The development of solid-state proton conductors with high proton conductivity at low temperatures is crucial for the implementation of hydrogen-based technologies for portable and automotive applications. Here, we report on the discovery of a new crystalline metal acid triphosphate, ZrH5 (PO4 )3 (ZP3), which exhibits record-high proton conductivity of 0.5-3.1×10-2 S cm-1 in the range 25-110 °C in anhydrous conditions. This is the highest anhydrous proton conductivity ever reported in a crystalline solid proton conductor in the range 25-110 °C. Superprotonic conductivity in ZP3 is enabled by extended defective frustrated hydrogen bond chains, where the protons are dynamically disordered over two oxygen centers. The high proton conductivity and stability in anhydrous conditions make ZP3 an excellent candidate for innovative applications in fuel cells without the need for complex water management systems, and in other energy technologies requiring fast proton transfer.

Anhydrous Superprotonic Conductivity in the Zirconium Acid Triphosphate ZrH5(PO4)3**

AbstractThe development of solid‐state proton conductors with high proton conductivity at low temperatures is crucial for the implementation of hydrogen‐based technologies for portable and automotive applications. Here, we report on the discovery of a new crystalline metal acid triphosphate, ZrH5(PO4)3 (ZP3), which exhibits record‐high proton conductivity of 0.5–3.1×10−2 S cm−1 in the range 25–110 °C in anhydrous conditions. This is the highest anhydrous proton conductivity ever reported in a crystalline solid proton conductor in the range 25–110 °C. Superprotonic conductivity in ZP3 is enabled by extended defective frustrated hydrogen bond chains, where the protons are dynamically disordered over two oxygen centers. The high proton conductivity and stability in anhydrous conditions make ZP3 an excellent candidate for innovative applications in fuel cells without the need for complex water management systems, and in other energy technologies requiring fast proton transfer.

Sulphur vs NH Group: Effects on the CO2 Electroreduction Capability of Phenylenediamine-Cp Cobalt Complexes.

The cobalt complex (I) with cyclopentadienyl and 2-aminothiophenolate ligands was investigated as a homogeneous catalyst for electrochemical CO2 reduction. By comparing its behavior with an analogous complex with the phenylenediamine (II), the effect of sulfur atom as a substituent has been evaluated. As a result, a positive shift of the reduction potential and the reversibility of the corresponding redox process have been observed, also suggesting a higher stability of the compound with sulfur. Under anhydrous conditions, complex I showed a higher current enhancement in the presence of CO2 (9.41) in comparison with II (4.12). Moreover, the presence of only one -NH group in I explained the difference in the observed increases on the catalytic activity toward CO2 due to the presence of water, with current enhancements of 22.73 and 24.40 for I and II, respectively. DFT calculations confirmed the effect of sulfur on the lowering of the energy of the frontier orbitals of I, highlighted by electrochemical measurements. Furthermore, the condensed Fukui function f - values agreed very well with the current enhancement observed in the absence of water.

Enhanced proton conductivity and power density of HT-PEMFCs using tin pyrophosphate microparticles-dispersed polybenzimidazole composite electrolyte membranes

Proton conductivity and acid retention property of PBI-based polymer electrolyte membrane is critical factor for high-temperature PEMFCs with high performance. The present study was undertaken in order to demonstrate the effect of SnP2O7 microparticles incorporation for the PBI-based membrane to the fuel cell performance. Besides, the correlation between dispersion property of additives and fuel cell performance was investigated, by taking the larger particle sizes of Sn-originated material into account. Highly dispersed SnP2O7 microparticles derived by the wet mechanochemical treatment has resulted in the novel PBI-based composite membrane with high-proton conductivity (4.17 mS cm−1 at 160 °C, anhydrous) and superior acid retention property. Consequently, the highest peak power density of 373 mW cm−2 at 160 °C under anhydrous conditions was achieved for the composite membrane with wet-mechanical milled SnP2O7, while the membrane without mechanochemical treatment showed lowest peak power density (168 mW cm−2) even inferior to the pure PBI membrane. Investigations into the PBI-based composite electrolyte membrane incorporated with highly dispersed SnP2O7 protonic conductive microparticles have yielded a performance enhancement of high-temperature PEMFCs.

New anhydrous proton exchange membranes based on polypyrrolone (PPy) for high-temperature polymer electrolyte fuel cells

Polypyrrolone (PPy) possesses excellent heat resistance and mechanical properties, moreover, the N-heterocycle contained in the PPy allows the absorption of phosphoric acid (PA) for proton conduction. In the present work, PPy is synthesized by a two-step method and evaluated for the first time as the polymeric material for high temperature proton exchange membranes (HT-PEMs). The PA-doped PPy membrane reaches a peak power density of 582 mW cm−2 at 160 °C under fully anhydrous conditions, besides, the fuel cell exhibits excellent durability over a period of 300 h with a load voltage decay of only 0.032% per hour and remains 0.647 V after the test. Further, the PPy-impregnated polyimide (PI) nanofiber mat composite membrane (PI@PPy) with an optimal thickness is fabricated with enhanced dimensional stability, of which acid swelling ratio noticeably declined by 51% in area and 25% in volume. A higher peak power density (634 mW cm−2) and less cell voltage reduction is also observed in the composite membrane, benefits from the trade–off between proton conductivity and PA retention ability. The results of the present study may contribute to further studies on polypyrrolone-based HT-PEMs and composite membranes.

Highly Elastic, Healable, and Durable Anhydrous High-Temperature Proton Exchange Membranes Cross-Linked with Highly Dense Hydrogen Bonds.

Proton exchange membranes (PEMs) with excellent durability and working stability are important for PEM fuel cells with extended service life and enhanced reliability. In this study, highly elastic, healable, and durable electrolyte membranes are fabricated by the complexation of poly(urea-urethane), ionic liquids (ILs), and MXene nanosheets (denoted as PU-IL-MX). The resulting PU-IL-MX electrolyte membranes have a tensile strength of ≈3.86MPa and a strain at break of ≈281.89%. The PU-IL-MX electrolyte membranes can act as high temperature PEMs to conduct protons under an anhydrous condition of the temperatures above 100°C. Importantly, the ultrahigh density of hydrogen-bond-cross-linked network renders PU-IL-MX membranes excellentIL retention properties. The membranes can maintain more than ≈98% of their original weight and show no decline of proton conductivity after being placed under highly humid conditions of ≈80°C and relative humidity of ≈85% for 10days. Moreover, due to the reversibility of hydrogen bonds, the membranes can heal damage under the working conditions of fuel cells to restore their original mechanical properties, proton conductivities, and cell performances.

Microwave-Assisted Rapid Substitution of Ti for Zr to Produce Bimetallic (Zr/Ti)UiO-66-NH2 with Congenetic "Shell-Core" Structure for Enhancing Photocatalytic Removal of Nitric Oxide.

Efficient nitric oxide (NO) removal without nitrogendioxide(NO2 )emission is desired for the control of air pollution. Herein, a series of (Zr/Ti)UiO-66-NH2 with congenetic shell-core structure, denoted as Ti-UION, are rapidly synthesized by microwave-assisted post-synthetic modification for NO removal. The optimal Ti-UION (i.e., 2.5Ti-UION) exhibits the highest activity of 80.74% without NO2 emission with moisture, which is 21.65% greater than that of the UiO-66-NH2 . The NO removal efficiency of 2.5Ti-UION further increases to 95.92% without photocatalyst deactivation under an anhydrous condition. This is because selectively produced NO2 in photocatalysis is completely adsorbed into micropores, refreshing active sites for subsequent reaction. In addition, the enhanced photocatalytic activity after Ti substitution is due to the presence of Ti electron acceptor, the potential difference between the shell and core of Ti-UION crystal, and the high conductivity of TiO units. Additionally, the improved adsorption of gas molecules not only favors NO oxidation, but also avoids the emission of NO2 . This work provides a feasible strategy for rapid metal substitution in metal-organic frameworks and insights into enhanced NO photodegradation.

Tranilast-matrine co-amorphous system: Strong intermolecular interactions, improved solubility, and physiochemical stability

There is a great interest to develop co-amorphous drug delivery systems to enhance the solubility of biopharmaceutics classification system (BCS) class II and IV drugs. However, most reported systems only resulted in severalfold solubility improvement. Tranilast (TRA) is an anti-allergic drug used to treat bronchial asthma and allergic rhinitis. It is a BCS class II drug and its poor aqueous solubility affects its absorption in vivo. To address this issue, a natural alkaloid matrine (MAR) with interesting biological activities was chosen to form a co-amorphous system with TRA, based on the solubility parameter and phase solubility experiment. The TRA-MAR drug-drug co-amorphous system was prepared by the solvent evaporation method, and further characterized by powder X-ray diffraction and modulated temperature differential scanning calorimetry. Fourier transform infrared spectroscopy, FT-Raman, and X-ray photoelectron spectroscopy revealed the formation of salt and the presence of strong intermolecular interactions in the TRA-MAR co-amorphous system, which are also supported by molecular dynamics simulations, showing ionic and hydrogen bonding interactions. This co-amorphous system exhibited excellent physical stability at both 25 °C and 40 °C under anhydrous silica gel condition. Finally, co-amorphous TRA-MAR showed greatly enhanced solubility (greater than 100-fold) and rapid release behavior in the vitro release experiments. NMR spectroscopy revealed the strong intermolecular interactions between TRA and MAR in both DMSO‑d6 and D2O. Our study resulted in a TRA-MAR co-amorphous drug system with significant solubility improvement and showcased the great potential to improve the dissolution behaviors of BCS class II and IV drugs through the co-amorphization approach.

Incorporation of Upconverting LiYF4:Yb3+, Tm3+ Nanoparticles with High Quantum Yield in TiO2 Metallogels for Near Infrared-Driven Photocatalytic Dye Degradation

By using anhydrous conditions, we report here an optimized synthesis of small but highly emitting upconverting nanoparticles (UCNPs) of LiYF4:Yb3+, Tm3+ without any surface passivation layers of silica or undoped matrix. For this, anhydrous precursors [Li(TFA)(monoglyme)] and [Ln(TFA)3(monoglyme)] (Ln = Y, Gd, Tm, Yb; TFA = trifluoroacetate) were synthesized via a facile one-pot synthetic protocol, which showed excellent thermal decomposition compatibility to afford Ln3+-doped LiLnF4 NPs by simultaneous decomposition in the solution phase. A detailed study of the influence of many key parameters such as the ratio of dopant ions and solvents, concentration of precursors, reaction time, and temperature over crystalline phase, size, shape, morphology, and upconverting properties of the NPs produced followed by a mechanism for the formation of LiYF4-based NPs is presented. The high quality of these NPs is manifested by the fact that their upconversion efficiency is quite comparable to that of a bulk single crystal of the same composition (bulk materials are believed to have far better UC performance due to low surface area and less defects). Successful incorporation of these UCNPs in transparent TiO2 metallogels provided an alternative strategy of highly homogeneous UCNP-TiO2 composites of variable composition (1–10% of NPs) having very high specific surface area (435–580 m2/g).

Proton-Conducting Polymeric Membranes Based on 1,2,4-Triazole

In this review, a comparative analysis of the literature and our own results obtained in the study of the physicochemical, dielectric, and proton-conducting properties of composite polymer materials based on 1H-1,2,4-triazole has been carried out. It has been established that 1H-1,2,4-triazole and homopolymers and copolymers of 1-vinyl-1,2,4-triazole are promising for the development of proton-conducting fuel cell membranes. They significantly improve the basic characteristics of electrolyte membranes, increase their film-forming ability, increase thermal stability up to 300-330 °C, increase the electrochemical stability region up to 3-4 V, promote high mechanical strength and morphological stability of membranes, and provide high ionic conductivity (up to 10-3-10-1 S/cm) under anhydrous conditions at temperatures above 100 °C. There is also an improvement in the solubility and a decrease in the glass transition temperature of polymers based on 1-vinyl-1,2,4-triazole, which facilitates the processing and formation of membrane films. The results obtained demonstrate the uniqueness of 1H-1,2,4-triazole and (co)polymers based on 1-vinyl-1,2,4-triazole and the promise of their use for the creation of heat-resistant plastic and electrochemically stable, mechanically strong proton-conducting membranes with high ionic conductivity under anhydrous conditions and at high temperatures.

Solvent-Free Mechanochemical Dense Pore Filling Yields CPO-27/MOF-74 Metal–Organic Frameworks with High Anhydrous and Water-Assisted Proton Conductivity

Proton-conducting solids operating in both anhydrous and humid conditions are of paramount importance for the development of fuel cells. We demonstrate that incorporating formamidinium or methylammonium ions in CPO-27/MOF-74 metal–organic frameworks renders them highly conductive under the two conditions. Highest proton conductivities reach 8 × 10–4 S/cm under anhydrous conditions, exceed 10–3 S/cm already at low relative humidity (30–50% RH) and low temperatures (25–60 °C), and reach 10–2 S/cm at 60 °C and 70% RH. The dense pore filling with the protic cations is enabled by solvent-free mechanochemistry and stoichiometric saturation of open metal sites (Mg, Ni) with thiocyanate ligands. DFT modeling reveals that high anhydrous proton conductivity is associated with the presence of water-free extended networks of hydrogen bonds along the [001] channel and together with electrochemical impedance measurements (EIS) shed light on the mechanism of proton transport.