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The optimal ratio of reaction solutions resulted in excellent performance and product selectivity of CuO/g-C3N4 composites in the photocatalytic CO2 reduction reaction. A pH-dependent chemical exchange saturation transfer (CEST) imaging nuclear magnetic resonance (NMR) method was used to confirm that CuO modification improves the adsorption capacity of CO2. [ABSTRACT FROM AUTHOR]

Amino acids are the building blocks of proteins and are widely used as important ingredients for other nitrogen‐containing molecules. Here, we report the sustainable production of amino acids from biomass‐derived hydroxy acids with high activity under visible‐light irradiation and mild conditions, using atomic ruthenium‐promoted cadmium sulfide (Ru1/CdS). On a metal basis, the optimized Ru1/CdS exhibits a maximal alanine formation rate of 26.0 molAla ⋅ gRu−1 ⋅ h−1, which is 1.7 times and more than two orders of magnitude higher than that of its nanoparticle counterpart and the conventional thermocatalytic process, respectively. Integrated spectroscopic analysis and density functional theory calculations attribute the high performance of Ru1/CdS to the facilitated charge separation and O−H bond dissociation of the α‐hydroxy group, here of lactic acid. The operando nuclear magnetic resonance further infers a unique "double activation" mechanism of both the CH−OH and CH3−CH−OH structures in lactic acid, which significantly accelerates its photocatalytic amination toward alanine. [ABSTRACT FROM AUTHOR]

Engineering surface-active facets of metal cocatalysts is one of the most widely explored strategies to develop advanced photocatalysts and promote photocatalytic solar energy conversion. Here, the surface-active facets of Pd nanocrystals in Pd/g-C 3 N 4 photocatalyst was related to the injection flow rate of PdCl 2. When PdCl 2 was injected at a low flow rate of 7.5 mL/h (7.5-Pd/g-C 3 N 4), the Pd nanocrystals were uniformly dispersed onto the g-C 3 N 4 with exposed low-index {100} and {111} surface-active facets. However, increasing the injection flow rate to 150 mL/h (150-Pd/g-C 3 N 4) formed Pd nanocrystals where only the {100} surface-active facet was exposed. Under visible light irradiation, the 7.5-Pd/g-C 3 N 4 nanocomposite exhibited excellent water splitting activity for hydrogen production (7.61 mmol g−1 h−1), which was significantly better than with the 150-Pd/g-C 3 N 4 nanocomposite (3.3 mmol g−1 h−1). Theoretical calculations and experimental results confirm the importance of the {111} surface-active facets in the 7.5-Pd/g-C 3 N 4 nanocomposite for promoting photocatalytic activity. [Display omitted] • The Pd/g-C 3 N 4 photocatalyst was prepared in a simple one-pot synthesis method. • The surface-active facets of Pd nanocrystals in Pd/g-C 3 N 4 was controlled by the injection flow rate of PdCl 2. • 7.5-Pd/g-C 3 N 4 nanocomposite exhibited excellent photocatalytic activity for H 2 production. • 7.5-Pd/g-C 3 N 4 nanocomposite also shown good performance in varied photocatalytic reactions. [ABSTRACT FROM AUTHOR]

A novel dodecanuclear Zr oxo cluster [Zr6O4(OH)4 (HSCH2CH2COO)12]2 (ZrO‐SH‐10) has been constructed under the room temperature, followed by oxidation of the sulfhydryl group with H2O2 to achieve a bifunctional catalyst with Lewis acid and Brönsted acid sites. The characterization of catalysts indicated that {Zr6O4} cluster core can be stabilized with a shell of carboxylate ligands, and the resulting ZrO‐SO3H was formed as a discrete molecular catalyst, exhibiting superior activity and recyclability for the cascade conversion of furfural to alkyl levulinate by the integration of transfer hydrogenation and alcoholysis in n‐butanol. The yield of n‐butyl levulinate can achieve as high as 91 % under the optimum conditions. Meanwhile, no leaching of the active species was found, which confirmed the structure of the Zr oxo cluster was air and moisture‐stable. On the basis of the studies on the reaction kinetics and isotope tracking, the reaction mechanism was proposed accordingly. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) have made great successes in clinical diagnosis, medical research, and neurological science. MRI provides high resolution anatomical images of tissues/organs, and MRS provides information of the functional molecules related to a specific tissue/organ. However, it is difficult for classic MRI/MRS to selectively image/probe a specific metabolite molecule other than the water or fat in tissues/organs. This greatly limits their applications on the study of the molecular mechanism(s) of metabolism and disease. Herein, we report a series of molecularly targeted MRI/MRS methods to target specific molecules. The optimal control method was used to efficiently prepare the singlet spin orders of varied multi-spin systems and in turn greatly expand the choice of the targeted molecules in the molecularly targeted MRI/MRS. Several molecules, such as N-acetyl-l-aspartic acid (NAA), dopamine (DA), and a tripeptide (alanine-glycine-glycine, AGG), have been used as targeted molecules for molecularly targeted MRI and MRS. We show in vivo NAA-targeted 1H MRS spectrum of a human brain. The high-resolution signal of NAA suggests a promising way to study important issues in molecular biology at the molecular level, e.g., measuring the local pH value of tissue in vivo, demonstrating the high potential of such methods in medicine. [ABSTRACT FROM AUTHOR]

The construction of efficient and stable non-noble metal bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) presents a challenge in electrocatalytic water splitting. CoS 2 is a promising electrocatalyst that could replace precious metals. In this work, a series of Co-MOF precursors having average particle sizes ranging from the nanometer to the micron scale (86–1084 nm) were synthesized in an unprecedented attempt; Co/CoS 2 heterojunction embedded in nitrogen doped carbon framework (Co/CoS 2 @NC) was prepared through further carbonization and sulfurization. The samples were characterized and evaluated by X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The results indicate that when the size of Co-MOF is less than 300 nm, the cubic structure framework easily collapses to form the spherical structure during the carbonization process. The catalytic activity of Co@NC is size-dependent; Co/CoS 2 @NC exhibited the best performance among the series, with an overpotential of 188 mV for HER and 349 mV for OER at a current density of 10 mA cm−2. This work provides experimental guidance for the design and synthesis of low-cost, efficient, and robust Co-based electrocatalysts. • With Co-MOF cubic nanoparticles as the precursor, Co/CoS 2 @NC was prepared through carbonization and sulfurization. • Co/CoS 2 @NC exhibited the best performance among the series. • The catalytic activity of Co@NC is size-dependent. • This work provides a guidance for the design and synthesis of low-cost, efficient, and robust Co-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Optically active and inactive hyperbranched polymers with specific thermoresponsive behaviours in water were reported. Through two steps hyperbranched polyethylenimine (HPEI) polymers terminated with different amount of D-phenylalanine (D-Phe), L-phenylalanine (L-Phe) or DL-phenylalanine (DL-Phe) were prepared and characterized. The analyses on the solution properties by turbidimetry, dynamic light scattering, fluorescence probe and H-NMR demonstrated that all the polymers exhibited specific thermoresponsive behaviours in water, including: (1) In the dilute polymer concentration region, increasing the polymer concentration led to the increase of phase transition temperature; (2) The optically inactive thermoresponsive hyperbranched polymers showed a higher cloud-point temperature ( T ) than their corresponding optically active ones in a relatively higher polymer concentration; (3) At the same polymer concentration the hydrophobic groups of the optically inactive HPEI-DL-Phe formed more perfect hydrophobic domain than those of the optically active HPEI-L-Phe and HPEI-D-Phe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Operando NMR combined with gas-probe method was used to study active sites transfer under the metal-support interaction. • The photocatalytic conversion efficiency of pure TiO 2 decreased, while that of Pt/TiO 2 was unaffected in gas conditions. • After loading metal-Pt, active sites changed from TiO 2 surface to Pt/TiO 2 interface. Recently metal-support interaction (MSI) has attracted considerable attention in photocatalysis. Some studies emphasize the importance of active sites on photocatalysts; however, there are no reports on site changes under MSI in real reactive conditions. Herein, an operando nuclear magnetic resonance technique was proposed to study such site changes on anatase TiO 2 and Pt/TiO 2 , through a gas-probe method, in CH 3 OH reforming. The photocatalytic oxidation efficiency of CH 3 OH by pure TiO 2 decreased immensely under extra-gas conditions, while that by Pt/TiO 2 was unaffected. The surface of pure TiO 2 were occupied by injected gas molecules, making CH 3 OH inaccessible to active sites. However, in Pt/TiO 2 , CH 3 OH adsorption sites changed from TiO 2 surface to metal-Pt/TiO 2 interface as confirmed by H 2 gas-probe experiments. This study provides a deeper understanding of active sites transfer by MSI and leverages the gas-probe method for its detection to guide the development of technology to test active-site positions in heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Nano-structuring and metal-support interactions are effective methods to improve the electrocatalytic activity of heterogeneous catalysis. In this study, we synthesized nitrogen-doped porous carbon substrates by using a SiO 2 -protected calcination strategy with ZIF-8 as a precursor. The experimental results revealed the prepared porous nitrogen-doped carbon (PNC) to have high dispersion, large specific surface area, and rich pore structure, allowing high exposure of active sites. The carbon support showed optimum characteristics to deposit precious metals with small particle sizes. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) showed that the N groups on the PNC substrates served as coordination sites for Ru, allowing the formation of ultrafine nanoclusters. The Ru clusters showed good metal dispersion, exposing more active sites and improving the utilization of the precious metal. At a current density of 10 mA/cm2, Ru/PNC showed a minimum overpotential of 40 mV. This work provided a simple and effective method for the preparation of excellent carbon substrates and the synthesis of metal clusters with small particle sizes. N-doped porous carbon (PNC) was synthesized by a SiO 2 -protected calcination strategy by using ZIF-8 as precursor. Compared with Ru/NC, the HER catalytic performance of Ru/PNC catalysts with Ru clusters has been significantly improved. [Display omitted] • Ru nanoclusters was prepared by the EG microwave-assisted method. • N-doped porous carbon was synthesized by a SiO 2 -protected calcination strategy. • Ru/PNC catalyst showed excellent HER-catalytic performance in acidic media. [ABSTRACT FROM AUTHOR]

In radiomics studies, researchers usually need to develop a supervised machine learning model to map image features onto the clinical conclusion. A classical machine learning pipeline consists of several steps, including normalization, feature selection, and classification. It is often tedious to find an optimal pipeline with appropriate combinations. We designed an open-source software package named FeAture Explorer (FAE). It was programmed with Python and used NumPy, pandas, and scikit-learning modules. FAE can be used to extract image features, preprocess the feature matrix, develop different models automatically, and evaluate them with common clinical statistics. FAE features a user-friendly graphical user interface that can be used by radiologists and researchers to build many different pipelines, and to compare their results visually. To prove the effectiveness of FAE, we developed a candidate model to classify the clinical-significant prostate cancer (CS PCa) and non-CS PCa using the PROSTATEx dataset. We used FAE to try out different combinations of feature selectors and classifiers, compare the area under the receiver operating characteristic curve of different models on the validation dataset, and evaluate the model using independent test data. The final model with the analysis of variance as the feature selector and linear discriminate analysis as the classifier was selected and evaluated conveniently by FAE. The area under the receiver operating characteristic curve on the training, validation, and test dataset achieved results of 0.838, 0.814, and 0.824, respectively. FAE allows researchers to build radiomics models and evaluate them using an independent testing dataset. It also provides easy model comparison and result visualization. We believe FAE can be a convenient tool for radiomics studies and other medical studies involving supervised machine learning. [ABSTRACT FROM AUTHOR]

Operando NMR has been exploited to probe the effects of photon flux and wavelength on photocatalytic reforming of methanol. • Operando NMR technique can be used to study the CH 3 OH photochemistry process. • CH 3 OH oxidation reaction could be enhanced by photon flux. • Photo energy had different effects on CH 3 OH photoreactions for TiO 2 and Pd/TiO 2. • SPR of the metal cocatalyst can be observed at 380 nm for the Pd/TiO 2 sample. • Operando NMR may help know the photoreactions in practical working conditions. Photocatalytic decomposition of water for hydrogen generation is a promising way to obtain clean energy sources, and photon flux together with photon energy play particularly important roles in photocatalytic reactions. However, a study of their effects under real conditions is still limited, thus leaving a gap in our understanding. Herein, an operando NMR technique was proposed to systematically study the effects of photon flux and photon energy on TiO 2 and Pd/TiO 2 -based photocatalytic methanol reforming reactions by changing the irradiation wavelength from 350 to 400 nm. Experimental results showed that the productivity of the methanol oxidation reaction can be obviously influenced by photon flux for the pure TiO 2 and Pd/TiO 2 sample, but longer wavelengths (lower photon energy) can slow down the reaction. Meanwhile, on the Pd/TiO 2 catalyst a significantly enhanced activity in CH 3 OH oxidation was found at the irradiation with the wavelength of 380 nm, which activity in CH 3 OH oxidation is even higher than that observed under the irradiation with the wavelength of 365 nm. This enhanced oxidation activity can be attributed to the surface plasmon resonance of the cocatalyst. [ABSTRACT FROM AUTHOR]

Operando NMR combined with the DFT calculations has been exploited to probe the crucial role of the bulk H 2 O in the CH 3 OH heterogeneous photochemistry processes on the surface of rutile-TiO 2. • Bulk H 2 O can significantly affect the CH 3 OH reforming products. • The participation ways of bulk H 2 O can vary from H 2 O molecule to H-atom. • The productivities of CH 3 OH reforming products vary with H 2 O concentration. • Operando NMR can be used to probe the kinetics of the CH 3 OH photocatalysis. Solid-liquid heterogeneous catalysis reactions play key roles in industrial catalytic reactions, throughout pollution control, fuel cell, methanol reforming and so on. But, few operando techniques have been performed to track the complex reaction processes, especially those in bulk liquid environment containing two or more liquid reactants, thus leaving a gap in our understanding of the reaction mechanisms deep into the working conditions. Here, we demonstrate an approach, using operando nuclear magnetic resonance (NMR) to probe the dynamics and kinetics of the methanol heterogeneous photochemistry processes in liquid condition with and without bulk water (H 2 O). It shows that not only can bulk H 2 O affect the types of methanol reforming products, but also its participation way can vary from H 2 O molecule to H-atom. Furthermore, the productivities of the main products - methylene glycol (HOCH 2 OH) and hemiacetal (CH 3 OCH 2 OH) – show different dependency on the H 2 O concentration, which is further supported by the density functional theory calculations (DFT). The operando NMR method opens up exciting opportunities for the mechanism studies of heterogeneous catalysis reaction in bulk liquid. [ABSTRACT FROM AUTHOR]

The temperature dependent morphologies of co-existing solid ice and interfacial water within two classic mesoporous materials, MCM-41 and SBA-15, are investigated below the Gibbs-Thomson transition temperature using Cryo-NMR, NMR spin-diffusion and NMR spectral analysis (second moment calculations). By using the combined NMR approach, the difference of the ice cores and interfacial water layers in MCM-41 and SBA-15 is unveiled. Based on the derived thickness of the interfacial water layers, the surface features in the two porous materials are discussed. The work demonstrates an approach to use the combined NMR techniques to study the porous material surface via probing the interfacial water layers, which can be used to study the physical/chemical properties of the material surface on the molecular level in general. Unlabelled Image • The morphologies of the solid ice and the interfacial water in porous materials are probed by NMR. • The thickness of the interfacial water layers in porous materials is measured. • The different interfacial water layers are attributed to the different surface features of the materials. • The NMR methods provide an approach to study the interfacial water layers of material in general. [ABSTRACT FROM AUTHOR]

Solid forms play a central role in modulating and optimizing the physicochemical properties of drugs, among which crystalline inclusion complexes (ICs) represent an emerging subcategory. In this study, we confirmed the inclusion of linear polymer polytetrahydrofuran (PTHF) into carbamazepine (CBZ) Form II, an extensively studied crystal structure with unique channel voids in its unsolvated form. According to solid-state NMR, PTHF chains were located in the CBZ channels with an extended conformation. Guest exchange experiments were performed on the toluene-solvated CBZ Form II by agitation in PTHF solution. The guest exchange kinetics was monitored by solution NMR, which agreed with the three-dimensional diffusion model. Further investigation revealed that the guest exchange only occurred on the free surface of the toluene-solvated CBZ Form II crystals via a recrystallization mechanism, leading to the formation of a core–shell structure with PTHF merely located in the shell layer. The shell crystal acted as the barrier layer that controlled the diffusion of molecules and consequently the extent of guest exchange, validating the fitted diffusion kinetic model. These results give insight into the guest exchange process between the small molecule guest and polymer guest in a drug IC crystal, and provide implications for a better understanding of guest selectivity and controlling the solid-state properties of drug crystals. [ABSTRACT FROM AUTHOR]

The distribution and dynamics of Li+ ions in β-CD-PEO/Li+ crystalline polymer electrolytes were investigated by 7Li-6Li REDOR NMR and variable-contact-time1H-6Li CP/MAS NMR. [Display omitted] • The distribution and dynamics of the Li+ ions in the crystalline polymer electrolytes (i.e., β-CD-PEO/Li+) were investigated by solid-state NMR. • 7Li-6Li TEDOR NMR was used to correlated the 6Li signals and the 7Li signals. • The 7Li-6Li dipolar couplings measured by 7Li-6Li REDOR provide a way to understand the Li+ spatial density in the samples. • The variable-contact-time cross 1H-6Li CP/MAS NMR was used to probe the dynamics of Li+ ions. • This work demonstrates possible future applications of solid-state NMR on the study of polymer electrolyte. In this work, the distribution and dynamics of Li+ ions in β-CD-PEO/Li+ (β-CD, β-cyclodextrin; PEO, polyethylene-oxides) crystalline polymer electrolytes were investigated by solid-state NMR to enlighten the ionic conduction mechanism. Specifically, 7Li-6Li REDOR NMR and variable-contact-time 1H-6Li CP/MAS NMR were adopted for the study. The results demonstrate that Li+ ions coordinated by polymer chains have relatively compact spatial density and fast dynamics, which facilitate the improvement of the electrochemical properties. Additionally, the variation of the distribution and dynamics of the Li+ ions and the ionic conduction mechanism were studied and discussed by altering the amount of the Li+ ions. This work deepens our understanding of the distribution and dynamics of Li+ ions in β-CD-PEO/Li+ crystals and demonstrates possible future applications of solid-state NMR on the study of the polymer electrolytes. [ABSTRACT FROM AUTHOR]

Chain packing in the non-crystalline region of a semi-crystalline polymer is strongly influenced by the crystallization conditions. Using a single-site catalytic system, deuterated Ultra High Molecular Weight Polyethylenes (UHMW-PEs) are synthesized and the chain topology of the noncrystalline region is investigated by solid-state NMR. The variability in chain packing within the noncrystalline region is introduced on crystallizing the same polymer either by controlled synthesis or solution or melt. 2 H NMR combined with line shape simulations yield detailed information on the geometry and frequency of the segmental motion in the noncrystalline regions of deuterated UHMWPE crystallized at three different conditions. High resolution solid-state 13 C NMR reveals the temperature dependence of the conformation statistics of chain segments in the noncrystalline regions of the samples. Combining the observations from the 2 H and 13 C NMR, the influence of segmental motions on the conformation statistics in the noncrystalline regions of the samples are discussed. [ABSTRACT FROM AUTHOR]

The detailed knowledge of the structure and dynamics in molecular level is very relevant for our understanding of the conductivity mechanism of solid state polymer electrolytes. In this work, we have synthesized two conductive β-CD-polyether/Li + inclusion crystals, which both have the channel-like structure formed by the β-CDs, but differ by the chemical nature of the assembled polymer chains. 1 H, 7 Li and 19 F solid state NMR have been performed to study the dynamics of the polymer chains, cations and anions. 1 H NMR of the samples reveals the clear difference in the segmental mobility of the polymer chains threaded inside the β-CDs, depending on the chemical nature of the polymer chains. Temperature dependent solid-state 2D 7 Li- 7 Li exchange NMR combined with 7 Li finite-pulse radio frequency-driven recoupling (fp-RFDR) NMR reveals two different Li + local exchange dynamics, namely, the Li + exchange process between the different polymer chain segments and the Li + exchange process between the polymer chains and the channels (i.e., the assembled β-CDs). 19 F NMR of the samples reveals that the anions in the samples are in a relatively immobile state, indicating that the anions are well separated from the mobile Li + ions in the samples. The implications of these NMR results for understanding of the conductivity mechanism of the materials are discussed. [ABSTRACT FROM AUTHOR]

The development of low-Pt catalysts is important for the large-scale application of Pt-based catalysts. Catalytic reactions mainly occur on the surface or interface of a material, and thus the surface properties of the catalyst will strongly affect their catalytic activity; this phenomenon has attracted widespread attention. Here, a series of Pt NPs with different chemical states and particle sizes were obtained by changing the light source wavelength, light time, and other conditions of light deposition synthesis. The Pt-TiO 2 catalyst has excellent potential in both photocatalytic hydrogen evolution (4.5 mmol·g−1·h−1) and electrocatalytic hydrogen evolution (26 mV@10 mA cm−2). We also found that the photocatalytic activity is more sensitive to the chemical state of Pt and that reducing the catalyst size can improve the electrocatalytic activity. This work not only provides a green and effective method to adjust the chemical state of precious metals on metal oxides but also helps to understand the impact of surface states on the catalytic process. A series of Pt NPs with different chemical states and sizes were embedded in TiO 2 (B) via a modified photochemical reduction method. The optimized Pt-TiO 2 (B) bifunctional catalyst exhibited excellent p-HER and e-HER catalytic activity. [Display omitted] • A series of Pt NPs with different chemical states and particle sizes were obtained by a photochemical strategy. • The optimized Pt-TiO 2 catalyst has excellent potential in both p-HER (4.5 mmol g−1 h−1) and e-HER (26 mV@10 mA cm−2). • The p-HER is more sensitive to the chemical state of Pt, and reducing the catalyst size improves the e-HER. • This work provides a new idea to promote catalytic activity by adjusting the catalyst's state and size. [ABSTRACT FROM AUTHOR]

[Display omitted] • A NMR method having the multiple-targeting signal selectivity was developed. • Optimal control was used to efficiently prepare singlet order of multiple-spin system. • Several targeted molecules and/or chemical groups were probed simultaneously. Selectively probing specific molecules in complex mixtures with nuclear magnetic resonance promises new insights into molecular structures or molecular interaction. Such a study often can be further facilitated when two or more objects in chemical moieties of interest can be precisely targeted. Herein, we proposed a novel method to implement the multiple-targeting signal selection by optimal control of the spin singlets of two or more targeted spin systems from one or more molecules. This method can endow the conventional nuclear magnetic resonance (NMR), magnetic resonance image (MRI) and magnetic resonance spectrum (MRS) with the multiple-targeting signal selectivity to selectively probe several targeted molecules and/or chemical groups simultaneously. [ABSTRACT FROM AUTHOR]

A dielectric constant transition is chemically triggered and thermally switched in (HPy)2[Na(H2O)Co(CN)6] ( 2, HPy=pyridinium cation) by single-crystal-to-single-crystal transformation and structural phase transition, respectively. Upon dehydration, (HPy)2[Na(H2O)2Co(CN)6] ( 1) transforms to its semi-hydrated form 2, accompanying a transition from a low-dielectric state to a high-dielectric state, and vice versa. This dielectric switch is also realized by a structural phase transition in 2 that occurs between room- and low-temperature phases, and which corresponds to high- and low-dielectric states, respectively. The switching property is due to the variation in the environment surrounding the HPy cation, that is, the hydrogen-bonding interactions and the crystal packing, which exert predominant influences on the dynamics of the cations that transit between the static and motional states. [ABSTRACT FROM AUTHOR]

A dielectric constant transition is chemically triggered and thermally switched in (HPy)2[Na(H2O)Co(CN)6] ( 2, HPy=pyridinium cation) by single-crystal-to-single-crystal transformation and structural phase transition, respectively. Upon dehydration, (HPy)2[Na(H2O)2Co(CN)6] ( 1) transforms to its semi-hydrated form 2, accompanying a transition from a low-dielectric state to a high-dielectric state, and vice versa. This dielectric switch is also realized by a structural phase transition in 2 that occurs between room- and low-temperature phases, and which corresponds to high- and low-dielectric states, respectively. The switching property is due to the variation in the environment surrounding the HPy cation, that is, the hydrogen-bonding interactions and the crystal packing, which exert predominant influences on the dynamics of the cations that transit between the static and motional states. [ABSTRACT FROM AUTHOR]

Highly conductive, crystalline, polymer electrolytes, β-cyclodextrin (β-CD)-polyethylene oxide (PEO)/LiAsF6 and β-CD-PEO/NaAsF6, were prepared through supramolecular self-assembly of PEO, β-CD, and LiAsF6/NaAsF6. The assembled β-CDs form nanochannels in which the PEO/X+ (X=Li, Na) complexes are confined. The nanochannels provide a pathway for directional motion of the alkali metal ions and, at the same time, separate the cations and the anions by size exclusion. [ABSTRACT FROM AUTHOR]

A molecular compass-like behaviour is found in a perovskite-type cage compound (HIm)2[KCo(CN)6] (HIm = imidazolium cation). The dynamic changes in the HIm cation from the static to rotating state along with the rearrangement of the host cage result in switchable and anisotropic dielectric constants. [ABSTRACT FROM AUTHOR]

A metal-cyanide framework undergoes a dehydration-rehydration triggered reversible single-crystal-to-single-crystal transformation. The resulting accordion-like contraction-expansion corresponds to a size change along the c axis as much as 24 %. This anisotropic response arises from the cooperativity among the water molecules, K ions, and CN groups between the unique two-dimensional bimetallic layers through weak interactions of hydrogen bonds and electrostatic (ionic) interactions. The key role of the water molecules in the dehydration-rehydration process is revealed by solid-state 1H NMR spectroscopy and dielectric measurements. [ABSTRACT FROM AUTHOR]

A new category of crystalline polymer electrolyte prepared by the supramolecular self-assembly of polyethylene oxide (PEO), α-cyclodextrin (α-CD), and LiAsF6 is reported. The polymer electrolyte consists of the nanochannels formed by α-CDs in which the PEO/Li+ complexes are confined. The nanochannels formed by α-CD provide the pathway for the directional motion of Li+ ions and at the same time prevent the access of the anions by size exclusion, resulting in good separation of the Li+ ions and the anions. The conductivity of the reported material is 30 times higher than that of the comparable PEO/Li+ complex crystal at room temperature. By using state-of-art solid-state NMR spectroscopy, the structure and dynamics of the material were investigated in detail. The dynamics of the Li+ ions was studied and correlated to the ionic conductivity of the material. [ABSTRACT FROM AUTHOR]

A new category of crystalline polymer electrolyte prepared by the supramolecular self-assembly of polyethylene oxide (PEO), α-cyclodextrin (α-CD), and LiAsF6 is reported. The polymer electrolyte consists of the nanochannels formed by α-CDs in which the PEO/Li+ complexes are confined. The nanochannels formed by α-CD provide the pathway for the directional motion of Li+ ions and at the same time prevent the access of the anions by size exclusion, resulting in good separation of the Li+ ions and the anions. The conductivity of the reported material is 30 times higher than that of the comparable PEO/Li+ complex crystal at room temperature. By using state-of-art solid-state NMR spectroscopy, the structure and dynamics of the material were investigated in detail. The dynamics of the Li+ ions was studied and correlated to the ionic conductivity of the material. [ABSTRACT FROM AUTHOR]

• In-situ nitrogen doping was achieved by one-step method, a series of Fe M (M = Pt, Pd, Ru, Rh) alloy electrocatalyst NPs with N-doped carbon coatings (Fe M @CN) was synthesized based on a noble metal doped Fe-MOF. • The optimal FePt@CN electrocatalyst demonstrates high electrocatalytic performance in an acidic electrolyte, with low overpotential, high mass activity, and excellent catalytic stability. • The optimal FeRu@CN electrocatalyst obtains an unexpectedly low overpotential of 18 mV in an alkaline electrolyte, which results in a current density of 10 mA cm−2 that is even better than a commercial Pt/C electrocatalyst with 20 wt% Pt loading. • The systematic study presented herein demonstrates that electrocatalysts suitable for different electrolytes can be found in the same alloy system, provides a universal and simple method for synthesizing transition and noble metal alloy electrocatalyst NPs that provides promising prospects for application in industrial electrolysis systems. The alloy catalyst formed by transition metal and a small amount of noble metal has become the most promising substitute for M-based (M = Pt, Pd, Ru, Rh) catalyst. However, due to the direct exposure of the metal core to the electrolyte, it is vulnerable to corrosion and oxidation, which in turn reduces the catalytic stability and is becoming a major obstacle to sustainable hydrogen production. The present work addresses this issue by developing a one-step immersion-adsorption-pyrolysis strategy for synthesizing FeM alloy nanoparticles with N-doped carbon coatings (FeM@CN) for use as electrocatalysts in the HER. The deliberately designed metal-organic framework material was used as the precursor of catalyst synthesis to achieve the carbon coatings and simultaneously the heteroatom in-situ doping for the alloy nanoparticles. The optimal FePt@CN demonstrates excellent catalytic stability and HER activity in an acidic electrolyte medium. The reactions obtain a small overpotential of 28 mV to achieve current densities of 10 mA cm−2, which are comparable to a high-performance commercial Pt/C electrocatalyst with a much higher Pt loading. The FeRu@CN also demonstrates an outstanding performance with an overpotential of only 18 mV to achieve a current density of 10 mA cm−2 in an alkaline medium. In-situ nitrogen doping was achieved by one-step method, a series of Fe M (M = Pt, Pd, Ru, Rh) alloy electrocatalyst NPs with N-doped carbon coatings (Fe M @CN) was synthesized based on a noble metal doped Fe metal organic framework. The systematic study presented herein demonstrates that electrocatalysts suitable for different electrolytes can be found in the same alloy system. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the locations and interactions of adsorbed water molecules within a porous COF material, TpPa-1. The TpPa-1 samples include the as-synthesized powder samples and the samples first subjected to compression at high pressure and then ground into a powder form. The investigation applies a variety of advanced solid-state NMR techniques. The results indicate that the adsorbed water molecules in the as-synthesized and compressed samples can exist in different locations and bonding states. Here, the adsorbed water molecules in the as-synthesized samples are found to be mainly located in the pore spaces and interact only loosely with the chemical groups of the material. In contrast, a proportion of the water molecules in the compressed samples enter into the interstices between the layers and interact with the amino groups and the carbonyl groups of the material. The relocation of the water molecules in the compressed samples provides a plausible explanation for the molecular origin of the water adsorption capability of TpPa-1. In addition, the revealed weak interactions between the water molecules and the chemical groups of TpPa-1 are correlated with the molecular origin of the high water permeance. Image 1 • Absorbded water in a COF material, TpPa-1, were investigated by solid state NMR. • Water mainly locate in the nanopores of the as-synthesized TpPa-1. • Water can enter into the interstices between the layers of the compressed TpPa-1. • The molecular origin of the water adsorption capability of TpPa-1 was revealed. • This investigation applied a variety of advanced solid-state NMR techniques. [ABSTRACT FROM AUTHOR]

The development of novel, noble metal-free semiconductor catalysts with high efficiency is of great importance for the degradation of organic compounds. Among them, amorphous materials have been extensively studied for their unique and commercially useful properties. Here, a completely amorphous, noble metal-free photocatalyst C3N4ZnxOy (x, y = 0.32–1.10) was successfully synthesized from urea and ZnO by a simple high-temperature polymerization method. As the Zn content increased, the short-range ordered structures of the amorphous samples were still retained, as revealed by XPS, FTIR, and ssNMR. Meanwhile, the -CN3 structures were observed to be gradually destroyed, which may make the amorphous state more favorable for photocatalytic reactions. Compared with g-C3N4, the amorphous samples showed significantly reduced intensities in the photoluminescence spectra, indicating that the recombination rate of the photo-generated charge carriers was greatly reduced. It was confirmed that the optimized sample (C3N4Zn0.61O0.61) achieved a photocatalytic efficiency of 86.1% in the degradation of tetracycline hydrochloride under visible light irradiation within 1 h. This is about 2 times higher than that of both g-C3N4 and ZnO. This study emphasizes the importance of the amorphous structure in photocatalytic reactions, and this synthetic strategy may provide an effective model for designing other novel catalysts. [ABSTRACT FROM AUTHOR]

Polyethylene oxide-based solid polymer electrolytes (SPEs) are of research interest because of their potential applications in all-solid-state Li+ batteries. However, despite their advantages in terms of compatibility with the electrodes and easy processing, polyethylene oxide (PEO)/Li+ complexes often suffer from low conductivity at room temperature. Understanding the conduction mechanism and, in turn, developing strategies to improve the conductivity have long been the main objectives underlying research into PEO/Li+ complex electrolytes. Here, we prepared several special PEO/Li+ complex samples where the PEO/Li+ complex structures were located on the surfaces of PEO crystals and consisted of high content chain ends. We found two different Li+ species in the PEO/Li+ complex structures via solid-state nuclear magnetic resonance (NMR). The 2D 7Li exchange NMR showed the exchange process between the different Li+ species. The exchange dynamics of the Li+ ions provide a molecular mechanism of the Li+ transportation in the surface of PEO crystal lamella, which is further correlated with the ionic conduction mechanism of the PEO/Li+ complex structure. [ABSTRACT FROM AUTHOR]

Ionic Conductivity of Beta- Cyclodextrin-Polyethylene-Oxide/Alkali-Metal-Salt Complex are presented.

A reversible single‐crystal‐to‐single‐crystal transformation is found in a metal–cyanide framework: [CH6N3]2[FeK2(H2O)6(CN)6]. The structure consists of a two‐dimensional bimetallic layer with K4Fe3 defective cubane units in which the guanidinium cations reside. Reversible dehydration and rehydration processes of the compound tuned by weak interactions lead to a uniaxial contraction–expansion cycle along the crystallographic c direction, corresponding to an accordion‐like behavior. See the Communication by Y.‐F. Yao, Z.‐M. Wang, W. Zhang et al. on page 8269 ff. for more details. [ABSTRACT FROM AUTHOR]