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Encapsulation of enzymes within porous materials has shown great promise for protecting enzymes from denaturation, increasing their tolerance to harsh environments and promoting their industrialization. However, controlling the conformational freedom of the encapsulated enzymes to enhance their catalytic performance remains a great challenge. To address this issue, herein, following immobilization of GOx and HRP on a thermo-responsive porous poly(styrene-maleic-anhydride-N-isopropylacrylamide) (PSMN) membrane, a GOx–HRP@PSMN@HZIF-8 composite was fabricated by encapsulating GOx–HRP@PSMN in hollow ZIF-8 (HZIF-8) with liposome (L) as the sacrificial template. The improved conformational freedom for enzymes arising from the hollow cavity formed in ZIF-8 through the removal of L enhanced the mass transfer and dramatically promoted the catalytic activity of the composite. Interestingly, at high temperature, the coiled PN moiety in PSMN provided the confinement effect for GOx–HRP, which also significantly boosted the catalytic performance of the composites. Compared to the maximum catalytic reaction rates (Vmax) of GOx–HRP@PSMN@LZIF-8, the free enzyme and GOx–HRP@ZIF-8, the Vmax of the GOx–HRP@PSMN@HZIF-8 composite exhibited an impressive 17.8-fold, 10.8-fold and 6.0-fold enhancement at 37 °C, respectively. The proposed composites successfully demonstrated their potential as catalytic platforms for the colorimetric detection of glucose in a cascade reaction. This study paves a new way for overcoming the current limitations of immobilizing enzymes in porous materials and the use of smart polymers for the potential fabrication of enzyme@polymer@MOF composites with tunable conformational freedom and confinement effect. [ABSTRACT FROM AUTHOR]

Oxygen redox (OR) chemistry has been an attractive topic in the field of high-energy lithium-ion batteries, as it enables extra storage of charge and boosts the capacity of highly potential layered Li-rich oxide (LLO) cathode materials. However, the OR reaction is usually irreversible during the electrochemical process, inducing severe performance degradation that sets an impenetrable barrier to the LLO applications. Over the last two decades, great efforts have been made to fundamentally understand the irreversibility of OR, finally reaching a consensus that it is deeply rooted in the structural features of LLOs. Although the structural mechanism is complex and still remains to be further clarified, the current findings of the structure–OR coupling have already inspired blooming optimistic expectations from structural perspectives. Herein, we systematically review the recent progress of the OR investigations in LLOs, with a special emphasis on deciphering the structure–OR coupling. Moreover, efficient structural control strategies for promoting the reversibility of OR are also introduced, followed by an outlook on future rational design and development of LLO materials. This comprehensive summary and perspective are expected to be helpful to promote further OR and LLO research. [ABSTRACT FROM AUTHOR]

Two isostructural pillar-layer MOFs (JNU-105 and JNU-105-(NH2)2) have been successfully synthesized. JNU-105-(NH2)2 exhibits a red-shifted luminescence "turn on" for formaldehyde without the interference from other VOCs and a detection limit of 1.87 ppb. In situ single-crystal transformation studies confirm the aminal formation on the pillar linker, which was attributed to the exclusive luminescence response toward formaldehyde. [ABSTRACT FROM AUTHOR]

In this study, we designed and tested fluorescent probe zy-2 for specific and responsive imaging of pyruvate kinase M2 (PKM2), which can be excited by 419 nm light. A 17-fold enhancement in the responsive emission upon zy-2's binding to PKM2 was observed, imaging of which was successfully recorded in a time- and concentration-dependent manner in PKM2-positive cells. Thus, we obtained a responsive fluorescent probe for the specific and sensitive detection of PKM2, which is innovative in design and applicable to the detection of cancer cells. [ABSTRACT FROM AUTHOR]

Gyroid materials have received considerable attention from scientists due to their beautiful structures and advanced functions. On the other side, metal–organic frameworks are inorganic–organic hybrid crystalline porous materials with atomic precision, and can provide good structural models and rich topologies for gyroid materials. In this review, we will briefly introduce the structures of gyroid metal–organic frameworks and their topologies. In addition, their applications in gas adsorption, catalysis, sensors, and luminescent materials are also discussed in detail. [ABSTRACT FROM AUTHOR]

Uniform distribution of Li2MnO3 and LiMO2 components in a Co-free Li-rich layered oxide is achieved by treating precursors with NH3·H2O, which expands the lattice parameter and promotes the activation of Li2MnO3, resulting in excellent electrochemical performance. What's more, it also contributes to the storage stability of Li-rich layered oxides. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of three pairs of isostructural zirconium- and hafnium-based homometallic metal–organic frameworks (MOFs, termed Zr-MOF-1 and Hf-MOF-1, Zr-MOF-2 and Hf-MOF-2, and Zr-MOF-3 and Hf-MOF-3) with respective scu, sqc, and flu topologies by using the aggregation-induced-emission (AIE) ligand H4BTTB (4,4′,4′′,4′′′-(pyrazine-2,3,5,6-tetrayl)tetrabenzoic acid). As expected, all of them display excellent luminescence properties, and their potential application in the detection of Cr2O72− has been extensively studied. Among them, Zr/Hf-MOF-2 exhibits the high adsorption capacity for Cr2O72− (153 mg g−1 and 149 mg g−1, respectively), while Zr/Hf-MOF-3 demonstrates exceptional sensitivity in the detection of Cr2O72−, and the limits of detection are calculated to be 0.013 μM and 0.019 μM, respectively. The values are comparable to those of the best-performing MOF materials reported so far. Significantly, single-crystal X-ray diffraction studies revealed the exact location and configuration of Cr2O72− inside Zr/Hf-MOF-2. To the best of our knowledge, this is the first example of Zr/Hf-MOFs with direct evidence showing that Cr2O72− is linked to the Zr/Hf oxide cluster by replacing its terminal H2O/OH− groups within the single crystal. [ABSTRACT FROM AUTHOR]

The effect of fluoride coatings, an effective approach to suppress HF corrosion, on the cycling stability of NCM523 cathodes is systematically studied. It is the first study to reveal that fluoride coatings significantly restrain interfacial reactions when, simultaneously, the fluoride suspension possesses an appropriate pH (near 4.0) and there is a small cation ionic radius. [ABSTRACT FROM AUTHOR]

Polynuclear silver clusters are described that unexpectedly transform from cyclic trinuclear complexes (CTCs) upon reacting with σ-donating phenylacetylene, featuring a noria-like conformation. The introduction of foreign copper ions leads to isomorphic bimetallic Ag/Cu clusters, with a boost in the photoluminescence quantum yield relative to the original silver clusters. [ABSTRACT FROM AUTHOR]

Dual-emitting MOF materials have been widely explored in recent years for their potential applications as ratiometric luminescent probes. However, most of these dichromatic MOFs were constructed through encapsulation of dye molecules, and ones with intrinsic dual-emission from ligands and/or metal ions are still rare. Herein, we report a novel Eu-MOF (1) composed of trinuclear europium clusters and 2,6-naphthalenedicarboxylate (NDC) linkers. It exhibits ratiometric luminescence behavior within a pH range of 4.00 to 3.00. On the basis of an in situ single-crystal to single-crystal transformation study, a mechanism is proposed for this pH-regulated luminescence switching, in which the tiny variations in Eu-O bond lengths disturb the energy transfer from the ligand to the metal and therefore diminish the "antenna effect". Specifically, the Eu–ONDC bond length is elongated and the Eu–Owater bond length is shortened with increasing acidity, resulting in a gradually reduced luminescence intensity of Eu3+ and gradually enhanced luminescence intensity of the NDC ligand at the same time. This unique luminescence switching property of 1 allows for quantitative detection of 3-nitropropionic acid (3-NPA), a toxic mycotoxin in moldy sugarcane. Moreover, a rapid, highly sensitive, and visualizable response to 3-NPA is demonstrated by using MOF-based test paper. [ABSTRACT FROM AUTHOR]

A family of polyhedral metal-imidazolate cages based on the flexible bi-imidazole ligand L and Cu2+ ions have been synthesized and characterized, featuring an unusual Cu10L8 bicapped square antiprism structure (or Johnson solids, J17) with an adaptable cavity. These metal–organic cages encapsulate anions, and they will expand or compress after they are filled with different-sized anions. [ABSTRACT FROM AUTHOR]

A series of cubic cobalt-imidazolate cages have been successfully synthesized via subcomponent self-assembly in different solvents under solvothermal conditions. The homovalent CoII and mixed-valence CoIII,II-imidazolate cages are assembled with control over the mixed solvent ratio of N,N-diethylformamide/ethanol, respectively. [ABSTRACT FROM AUTHOR]

Catalytic oxidation of formaldehyde with non-noble metal catalysts is desirable yet still challenging. In this work, we describe a hard template method in combination with an in situ chelating strategy to construct a novel three-dimensionally structured CeO2-based composite which contains CeO2 quantum dots of 1.5–2.5 nm size anchored on nitrogen doped hierarchical porous carbon with both macropores and mesopores. When used as an oxidation catalyst, complete oxidation of formaldehyde could be achieved at a temperature 130 °C lower than that of bulk nano-CeO2 catalyst. The significantly improved catalytic activity could be attributed to the higher amount of oxygen vacancies and enhanced redox properties of CeO2 quantum dots as well as the three-dimensional porous texture. [ABSTRACT FROM AUTHOR]

In contrast to the regular postsynthetic modification (PSM) approach which is global and random in principle, a diffusion-controlled PSM strategy utilizing size mismatch between pores and reactants has been developed to target selective functionalization and fine-tuning of material performance. Demonstrating through narrow-pore ZIF-90 reacting with amines of contrasting aliphatic chain lengths, we manage to regulate the extent and distribution of hydrophobic functionalization, and to judiciously tune the hydrophobicity of the crystalline materials. A subtle balance between reagent dose, water tolerance enhancement, and maintenance of gas adsorption performance has been achieved. ZIF-90 crystallites are imparted with surface hydrophobicity by only 1% aliphatic modification of ligands, while its hydrothermal stability is enhanced by 5% aliphatic modification, owing to the coverage of the vulnerable mesopore regions in the overall structure. Moreover, such low-dose PSM avoids severe pore blockage which would result in significant repellence of gas/vapor adsorbates (e.g. N2, CO2, H2O), as also predicted by ideal adsorbed solution theory (IAST), showing largely unaffected CO2/N2 and CO2/CH4 separation performance. This proposed spatially-differentiated strategy provides a facile route to implementing diffusion-limited PSM processes to fabricate core–shell-like MOFs. [ABSTRACT FROM AUTHOR]

In this work, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (F-EPE), a kind of non-flammable hydrofluoroether, was initially mixed with lithium bis(oxalato)borate (LiBOB) and gamma-butyrolactone (GBL) to formulate a safe electrolyte for lithium-ion batteries. It was found that the addition of F-EPE endowed this novel electrolyte with a high safety level, low surface tension and good wettability to the separator and electrodes. More importantly, this safe electrolyte supported the graphite/LiCo1/3Mn1/3Ni1/3O2 full cell in achieving excellent electrochemical performances. During the prolonged cycle test at room temperature, its capacity retention after 500 cycles could reach 80.6%, which was comparable to that of a commercial electrolyte. Its rate performance at room temperature and cycle performance at elevated temperature (60 °C) surpassed those of the commercial electrolyte. In particular, its low-temperature performance was remarkable, and the cell could deliver a capacity as high as 74.2 mA h g−1 at −40 °C. In view of these results, such a safe electrolyte showed tremendous potential for practical application. [ABSTRACT FROM AUTHOR]

As promising cathodes for high-energy Li-ion batteries, the commercial application of layered Li-rich transition-metal oxides (LROs) is significantly prevented by their non-ideal cycling stability and rate capability. In this work, Li1.23Mn0.46Ni0.15Co0.16O2 samples are prepared by combining a solvothermal process and a Li2CO3 molten-salt method. When the molar ratio of Li2CO3 to transition-metal ions is 4 : 1, the obtained sample has the best electrochemical performance. Its initial discharge capacities at 20 and 300 mA g−1 are larger than 307.8 and 232.2 mA h g−1, respectively. After 200 cycles, the capacity retention ratio at 300 mA g−1 is still as large as 85.3%. In addition, we discovered that the relative content of lithium on the particle surface of the samples is more than that in the particle interior, and this distribution behavior of lithium is adjustable. In particular, we demonstrate for the first time that the overmuch enrichment of lithium on the particle surface will hinder the diffusion of Li-ions. This is the blockade effect of surface lithium, and this blockade effect can be alleviated by the Li2CO3 molten-salt method. This is the reason that the electrochemical performance of LROs can be greatly improved by the Li2CO3 molten-salt method. [ABSTRACT FROM AUTHOR]

A novel solvothermal-precursor method is designed to prepare uniform assembled microspherical LiMO2 (layered Li transition metal oxide) cathodes for high energy and power Li-ion batteries. The LiMO2 assembled microspheres exhibit superior long-term cycle stability and rate capability. [ABSTRACT FROM AUTHOR]

A mixture of diethylene glycol diethylether and non-flammable methyl-nonafluorobutyl ether was introduced as a new electrolyte for lithium ion batteries. And a fluoroethylene carbonate additive was used in this electrolyte to improve the compatibility with the graphite anode. The non-flammability and high flash point of this electrolyte indicated its high safety. This electrolyte had low viscosity and its conductivity reached 3.8 mS cm−1 at 25 °C. Graphite/LiFePO4 coin cells with commercial electrodes were utilized to evaluate the performances of the electrolyte. The rate, cycle and low-temperature performances of the graphite/LiFePO4 cells using this electrolyte were close to those of the cells using the conventional electrolytes with and without the fluoroethylene carbonate additive. These results indicated that this kind of safe electrolyte based on non-flammable hydrofluoroethers and solvents with a high flash point has great potential for practical application. [ABSTRACT FROM AUTHOR]

Lithium batteries for UPS, portable electronics and electrical vehicles rely on high-energy cathodes. Li-rich manganese-rich oxide (xLi2MnO3·(1 −x)LiMO2, M = transition metals) is one of the few materials that might meet such a requirement, but it suffers from poor energy retention due to serious voltage and/or capacity fade, which challenges its applications. Here we show that this challenge can be addressed by optimizing the interactions between the components Li2MnO3 and LiMO2 in the Li-rich oxide (i.e. stabilizing the layered structure through Li2MnO3 and controlling Li2MnO3 activation through LiMO2). To realize this synergistic effect, a novel Li2MnO3-stabilized Li1.080Mn0.503Ni0.387Co0.030O2 was designed and prepared using a hierarchical carbonate precursor obtained by a solvo/hydro-thermal method. This layered oxide is demonstrated to have a high working voltage of 3.9 V and large specific energy of 805 W h kg−1 at 29 °C as well as impressive energy retention of 92% over 100 cycles. Even when exposed to 55 °C, energy retention is still as high as 85% at 200 mA g−1. The attractive performance is most likely the consequence of the balanced stability and specific energy in the present material, which is promisingly applicable to other Li-rich oxide systems. This work sheds light on harnessing Li2MnO3 activation and furthermore efficient battery design simply through compositional tuning and temperature regulation. [ABSTRACT FROM AUTHOR]

The thermoelectric properties and the electronic structure of Sr5Sn2As6 were studied according to the first principles and semi-classical Boltzmann theory. To elucidate the thermoelectric performance of Sr5Sn2As6, we simulated its carrier concentration, Seebeck coefficient, and electrical conductivity, and provided an estimated value for the thermoelectric figure of merit ZT. For pure Sr5Sn2As6, the largest Seebeck coefficient (S) is 248 (mV K-1) at 500 K, and the minimum S is 202 (mV K-1) at 1200 K. The large Seebeck coefficient over a wide temperature range most likely results from the appropriate band gap (0.55 eV) of Sr5Sn2As6. By studying the carrier concentration dependence of the transport properties, the ZT value for p-type doping was found to be ~1.4 times that of n-type doping, which is mainly due to the larger effective mass of the valence band. Moreover, for n-type doping, both the Seebeck coefficient and the electrical conductivity along the z-direction are much larger than those along the other directions, due to the large band degeneracy and the light band, which results in a highest ZT value of 3.0 along the z-direction, with a carrier concentration of 9.4 x 1019 electrons per cm3 at 950 K. The highest ZT value for p-type along the z-direction is 1.7, with a carrier concentration of 1.2 x 1020 holes per cm3 at 950 K. Meanwhile, the minimum lattice thermal conductivity of Sr5Sn2As6 is small (0.47 W m_1 K_1), and is comparable to those of Ca5M2Sb6 (M -- Al, Ga, In). Hence, good thermoelectric performance along the z-direction for n-type Sr5Sn2As6 was predicted. [ABSTRACT FROM AUTHOR]

Owing to the merits of high capacity and low cost, Li-rich layered composite cathode materials have received extensive attention. Nevertheless, such materials always suffer from a poor rate capability, which seriously hinders their widespread practical applications. In this work, Li1.2Mn0.4Co0.4O2 composites were fabricated by a gel-combustion method, in which lithium carbonates formed by an in situ burning reaction were homogeneously mixed with metal oxides, leading to excellent electrochemical properties. The sintering temperature and time were optimized to 900 °C and 15 h. The samples prepared at optimum conditions exhibited a high discharge capacity and excellent rate capability. At a current density of 20 mA g−1, the specific discharge capacity was 310.5 mA h g−1 for the first cycle and the capacity retention was 75.8% after 30 cycles. When the current densities increase by 10 times to reach 200 mA g−1, the initial discharge capacity is still as high as 241.4 mA h g−1, superior to that of 203 mA h g−1 at the same current density reported previously by the oxalate-precursor method. Even when the current densities increase by 20 times, the capacity remained as high as 203.7 mA h g−1, and the capacity retention was 79.4% over 30 cycles. The high discharge capacity and improved rate capability of the optimized sample were beneficial with a perfect layered structure with c/a >5.0, appropriate particle size of about 450 nm, high lithium ion diffusion coefficient around 1.42 × 10−13 cm2 s−1, and the presence of a maximum content of Mn3+ (11.6%), as determined by XPS. The preparation method reported herein may provide hints for obtaining various advanced Li-rich layered composite materials for use in high-performance energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

We initiated a self-adjusted oxygen-partial-pressure approach to prepare high-performance Li2MnO3–LiMO2 cathode material. Four different lithium resources, lithium acetate, lithium hydrate, lithium carbonate, and lithium nitrate were used to create the local oxygen partial pressure over the samples. Since the melting points or decomposition temperatures for these lithium resources decrease in a sequence, Li2CO3≈ LiOH ＞ LiNO3 ＞ CH3COOLi, the oxygen partial pressure of the four crucibles that contain these lithium salts increases in a sequence, S4 ≈ S3 ＜ S2 ＜ S1 ≈ air in muffle furnace (S1: CH3COOLi·2H2O, S2: LiNO3, S3: LiOH·H2O, and S4: Li2CO3). Regardless of the lithium resources, the decomposed gases reduced the local oxygen partial pressures, leading to an incomplete oxidation of Mn ions in the final product Li[Li0.14Mn0.47Ni0.25Co0.14]O2. That is, some of the Mn3+ ions existed in the final product Li[Li0.14Mn0.47Ni0.25Co0.14]O2, and the amount of Mn3+ ions was closely related to the oxygen partial pressure. The lower oxygen partial pressure gave rise to a larger amount of Mn3+ in the final products, as confirmed by X-ray photoelectron spectroscopy. Electrochemical tests showed that the products prepared using lithium carbonate exhibited the best electrochemical performance: the initial discharge capacity was 279.4 mA h g−1 at a current density of 20 mA g−1, which remained as high as 187.2 mA h g−1 even at a much higher current density of 500 mA g−1. Such excellent electrochemical performance could be ascribed to the presence of Mn3+ that decreased the surface layer resistance and charge transfer resistance, and that further increased the conductivity and Li+ ion diffusion coefficient. [ABSTRACT FROM AUTHOR]

Pd-catalysed decarboxylative Suzuki reactions and orthogonal Cu-based O-arylation reactions of aromatic carboxylic acids are reported. The new reactions may provide alternative routes for the synthesis of some biaryls and aromatic carboxylic esters. [ABSTRACT FROM AUTHOR]

The efficient separation of acetylene (C 2 H 2 ) from its mixture with carbon dioxide (CO 2 ) remains a challenging industrial process due to their close molecular sizes/shapes and similar physical properties. Herein, we report a microporous metal-organic framework (JNU-4) with square-planar mononuclear copper(ii) centers as nodes and tetrahedral organic linkers as spacers, allowing for two accessible binding sites per metal center for C 2 H 2 molecules. Consequently, JNU-4 exhibits excellent C 2 H 2 adsorption capacity, particularly at 298 K and 0.5 bar (200 cm 3 g -1 ). Detailed computational studies confirm that C 2 H 2 molecules are indeed predominantly located in close proximity to the square-planar copper centers on both sides. Breakthrough experiments demonstrate that JNU-4 is capable of efficiently separating C 2 H 2 from a 50 : 50 C 2 H 2 /CO 2 mixture over a broad range of flow rates, affording by far the largest C 2 H 2 capture capacity (160 cm 3 g -1 ) and fuel-grade C 2 H 2 production (105 cm 3 g -1 , ≥98% purity) upon desorption. Simply by maximizing accessible open metal sites on mononuclear metal centers, this work presents a promising strategy to improve the C 2 H 2 adsorption capacity and address the challenging C 2 H 2 /CO 2 separation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The strategy of aggregation-induced emission enhancement (AIEE) has been proven to be efficient in wide areas and has recently been adopted in the field of metal nanoclusters. However, the relationship between atomically precise clusters and AIEE is still unclear. Herein, we have successfully obtained two few-atom heterometallic gold-silver hepta-/decanuclear clusters, denoted Au6Ag and Au9Ag , and determined their structures by X-ray diffraction and mass spectrometry. The nature of the Au I ⋯Ag I interactions thereof is demonstrated through energy decomposition analysis to be far-beyond typical closed-shell metal-metal interaction dominated by dispersion interaction. Furthermore, a positive correlation has been established between the particle size of the nanoaggregates and the photoluminescence quantum yield for Au6Ag , manifesting AIEE control upon varying the stoichiometric ratio of Au : Ag in atomically-precise clusters., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Polynuclear silver clusters are described that unexpectedly transform from cyclic trinuclear complexes (CTCs) upon reacting with σ-donating phenylacetylene, featuring a noria-like conformation. The introduction of foreign copper ions leads to isomorphic bimetallic Ag/Cu clusters, with a boost in the photoluminescence quantum yield relative to the original silver clusters.

A family of polyhedral metal-imidazolate cages based on the flexible bi-imidazole ligand L and Cu 2+ ions have been synthesized and characterized, featuring an unusual Cu 10 L 8 bicapped square antiprism structure (or Johnson solids, J 17 ) with an adaptable cavity. These metal-organic cages encapsulate anions, and they will expand or compress after they are filled with different-sized anions.

The treatment of persistent infections often requires a high local drug concentration and sustained release of antimicrobial agents. This paper proposes the use of novel electrospinning of poly(lactic acid) (PLA) fibers containing uncoated and encapsulated chlorhexidine particles. Chlorhexidine particles with a mean (SD) diameter of 17.15 ± 1.99 μm were fabricated by the precipitation of chlorhexidine diacetate with calcium chloride. Layer-by-layer (LbL) encapsulation of the chlorhexidine particles was carried out to produce encapsulated particles. The chlorhexidine particles had a high chlorhexidine content (90%), and when they were electrospun into PLA fibers a bead-in-string structure was obtained. The chlorhexidine content in the fibers could be tuned and a sustained release over 650 h was produced, via chlorhexidine particle encapsulation. Chlorhexidine release was governed by the polyelectrolyte multilayer encapsulation as demonstrated by SEM and confocal imaging. The incorporation of uncoated and encapsulated chlorhexidine particles (0.5% and 1% wt/wt chlorhexidine) into the fibers did not cause toxicity to healthy fibroblasts or affect cell adhesion to the fibers over a period of 5 days. The chlorhexidine-containing fibers also demonstrated sustained antibacterial activity against E. coli via an agar diffusion assay and broth transfer assay. Therefore, the chlorhexidine-containing PLA fibers may be useful in the treatment of persistent infections in medicine and dentistry.