Improving the hydrothermal stability of Al-rich Cu-SSZ-13 zeolite via Pr-ion modification.

Al-rich (Si/Al = 4-6) Cu-SSZ-13 has been recognized as one of the potential catalysts to replace the commercial Cu-SSZ-13 (Si/Al = 10-12) towards ammonia-assisted selective catalytic reduction (NH3-SCR). However, poor hydrothermal stability is a great obstacle for Al-rich zeolites to meet the catalytic applications containing water vapor. Herein, we demonstrate that the hydrothermal stability of Al-rich Cu-SSZ-13 can be dramatically enhanced via Pr-ion modification. Particularly, after high-temperature hydrothermal aging (HTA), CuPr1.2-SSZ-13-HTA with an optimal Pr content of 1.2 wt% exhibits a T80 (temperature window of NO conversion above 80%) window of 225-550 °C and a T90 window of 250-350 °C. These values are superior to those of Cu-SSZ-13-HTA (225-450 °C for T80 and no T90 window). The results of X-ray diffraction Rietveld refinement, electron paramagnetic resonance (EPR) and spectral characterization reveal that Pr ions mainly located in the eight-membered rings (8MRs) in SSZ-13 zeolite can inhibit the generation of inactive CuOx during hydrothermal aging. This finding is further supported by density functional theory (DFT) calculations, which suggest that the presence of Pr ions restrains the transformation from Cu2+ ions in 6MRs into CuOx, resulting in enhanced hydrothermal stability. It is also noted that an excessive amount of Pr ions in Cu-SSZ-13 would result in the production of CuOx that causes the decline of catalytic performance. The present work provides a promising strategy for creating a hydrothermally stable Cu-SSZ-13 zeolite catalyst by adding secondary metal ions.

Biological Transformation of AgI on MOF-on-MOF-Derived Heterostructures: Toward Polarity-Switchable Photoelectrochemical Biosensors for Neuron-Specific Enolase.

The sensitive detection of neuron-specific enolase (NSE) as a biomarker for lung cancer at an early stage is critical but has long been a challenge. The emergence of polarity-switchable photoelectrochemical (PEC) bioanalysis has opened up new avenues for developing highly sensitive NSE sensors. In this study, we present such a biosensor depending on the bioinduced AgI transition on MOF-on-MOF-derived semiconductor heterojunctions. Specifically, treatment of ZnO@In2O3@AgI by bioproduced H2S can in situ generate the ZnO@In2O3@In2S3@Ag2S heterojunction, with the photocurrent switching from the cathodic to anodic one due to the changes in the carrier transfer pathway. Linking an NSE-targeted sandwich immunorecognition with labeled alkaline phosphatase (ALP) catalyzed generation of H2S, such a phenomenon was correlated to NSE concentration with good performance in terms of selectivity and sensitivity and a low detection limit of 0.58 pg/mL. This study offered a new perspective on the use of MOF-on-MOF-derived heterostructures for advanced polarity-switchable PEC bioanalysis.

Metal-organic framework-derived nitrogen-doped carbon-confined CoSe2 anchored on multiwalled carbon nanotube networks as an anode for high-rate sodium-ion batteries.

Metal selenides, as potential alternative candidates for sodium storage, have promising applicability due to their high theoretical specific capacity. However, their huge volume change and sluggish electrode kinetics during sodium ion uptake and release processes can result in insufficient cycling life and inferior rate performance, hindering their practical application. Herein, nitrogen (N)-doped carbon-confined cobalt selenide anchored on multiwalled carbon nanotube networks (denoted as CoSe2@NC/MWCNTs) was designed and successfully built through a selenization process with ZIF-67 MOF as the template. The existence of the interconnected MWCNT network plays a crucial role in not only enhancing the electronic conductivity and ion/electron-transfer efficiency but also ensuring structural stability. Consequently, the optimized CoSe2@NC/MWCNTs composite delivers a high reversible capacity of 479.6 mA h g-1 at a current rate of 0.2 A g-1, accompanied by a 92.0% capacity retention over 100 cycles and a predominant rate performance of 227.4 mA h g-1 even under 20 A g-1 when examined as the anode in Na-ion batteries. Moreover, the kinetic behaviors were confirmed using CV profiles at various rates, as well as the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). Besides, the HRTEM images clearly reveal the sodium-ion storage mechanism of the CoSe2 hybrid. These results make CoSe2@NC/MWCNTs a prospective anode material in advanced sodium-ion batteries.

Three-dimensional microspheres constructed with MoS2 nanosheets supported on multiwalled carbon nanotubes for optimized sodium storage.

Molybdenum disulfide (MoS2) has been regarded as a promising anode material in the field of sodium-ion batteries (SIBs), with the advantages of high theoretical capacity and large interlayer spacings. Unfortunately, its intrinsic poor electrical conductivity and large volume changes during the sodiation/desodiation reactions still limit its practical application. To deal with this shortcoming, we built MoS2 nanosheet/multiwalled carbon nanotube (denoted as MoS2-MSs/MWCNTs) composites with a three-dimensional (3D) micro-spherical structure, assembled in situ from MoS2 nanosheets. These nanosheets are connected to each other by the MWCNTs network, which provides a highly conductive pathway for electrons/ions through interparticle and intraparticle interfaces, accelerating charge transfer and ion diffusion capabilities. More importantly, the carbon network can boost electrical conductivity and relieve structural strain. Consequently, the as-prepared MoS2-MSs/MWCNTs composite presents a high reversible specific capacity of 519 mA h g-1 at 0.1 A g-1 after 100 cycles with a capacity retention of 94.4% and excellent rate performance (227 mA h g-1 at 10 A g-1). Outstanding cycling stability was also achieved (327.1 mA h g-1 over 1000 cycles at 2 A g-1) and was characterized by scanning electron microscopy (SEM) analysis. Our findings provide a simple and effective strategy to explore anode materials with advanced sodium storage properties.

Exploiting Polythiophenyl-Triazine-Based Conjugated Microporous Polymer with Superior Lithium-Storage Performance.

Conjugated microporous polymers (CMPs) have been heralded as promising energy-storage materials with advantages such as chemical flexibility, porous structure, and environmentally friendliness. Herein, a novel conjugated microporous polymer was synthesized by integrating triazine, thiophene, and benzothiadiazole into a polymer skeleton, and the Li+ -storage performance for the as-synthesized polymer anode in Li-ion batteries (LIBs) was investigated. Benefiting from the inherent large surface area, plentiful redox-active units, and hierarchical porous structure, the polymer anode delivered a high Li+ storage capacity up to 1599 mAh g-1 at a current rate of 50 mA g-1 with an excellent rate behavior (363 mAh g-1 at 5 A g-1 ) and a long-term cyclability of 326 mAh g-1 over 1500 cycles at 5 A g-1 , implying that the newly developed polymer anode offers a great prospect for next-generation LIBs.

Direct Z-scheme 1D/2D WO2.72/ZnIn2S4 hybrid photocatalysts with highly-efficient visible-light-driven photodegradation towards tetracycline hydrochloride removal.

There are increasing environmental concerns of serious pollution from emission of antibiotic wastewater. Herein, a series of direct Z-scheme WO2.72/ZnIn2S4 (WOZIS) hybrid photocatalysts composed of one-dimensional (1D) WO2.72 (WO) nanorods and two-dimensional (2D) ZnIn2S4 (ZIS) nanosheets have been designed and constructed for tetracycline hydrochloride (TCH) degradation without presence of solid-state electron mediators. The crystalline phase, chemical composition, morphology, optical properties and photocatalytic activity of the as-prepared samples were characterized by the XRD, XPS, SEM, HRTEM, BET, UV-vis DRS, and PL. Obviously, all the WOZIS hybrid photocatalysts exhibited significantly enhanced photocatalytic activity towards TCH degradation. Meanwhile, WOZIS-1 sample with WO/ZIS molar ratio of 1:1 showed the highest photocatalytic activity. The significantly enhanced photoactivity of WOZIS hybrid photocatalyst was due to Z-scheme charge separation mechanism based on the build of tight interfacial contacts between WO nanorods and ZIS nanosheets, thereby driving efficient charge separation. Moreover, the high photocatalytic stability of as-prepared WOZIS-1 hybrid sample was revealed through seven successive cycling reactions.

Bisulfone-Functionalized Organic Polymer Photocatalysts for High-Performance Hydrogen Evolution.

Conjugated polymers show great potential in the application of photocatalysis, particularly for the photoreduction reaction of water to generate hydrogen. Molecular structure design is a key part for building a high-performance organic photocatalyst. Herein, two bisulfone-containing conjugated polymer photocatalysts were constructed with 1D or 3D polymer structures, and the effect of polymer geometry on photocatalytic activity was studied. It was found that the linear polymer PySEO-1 exhibited increased photocatalytic performance compared with the 3D polymer network PySEO-2 because the enhanced coplanarity of the polymeric chain in PySEO-1 promoted the photogenerated charge-carrier transmission along the 1D main chain. As a result, an attractive hydrogen generation rate of 9477 µmol h-1 g-1 was obtained with PySEO-1 under broadband light irradiation. PySEO-1 also exhibited a high external quantum efficiency of 4.1 % at an incident light wavelength of 400 nm, demonstrating that the bisulfone-containing polymers are attractive as organic photocatalysts for hydrogen production.

Insight into Ion Transfer through the Sub-Nanometer Channels in Zeolitic Imidazolate Frameworks.

A crack-free sub-nanometer composite structure for the study of ion transfer was constructed by in situ growth of ZIF-90 [Zn(ICA)2 , ICA=Imidazole-2-carboxaldehyde] on the tip of a glass nanopipette. The potential-driven ion transfer through the sub-nanometer channels in ZIF-90 is strongly influenced by the pH of the solution. A rectification ratio over 500 is observed in 1 m KCl solution under alkaline conditions (pH 11.58), which is the highest value reported under such a high salt concentration. Fluorescence experiments show the super-high rectification ratio under alkaline conditions results from the strong electrostatic interaction between ions and the sub-nanometer channels of ZIF-90. In addition to providing a general pathway for further study of mass-transfer process through sub-nanometer channels, the approach enable all kinds of metal-organic frameworks (MOFs) to be used as ionic permselectivity materials in nanopore-based analysis.

Highly Efficient Oxygen Reduction Electrocatalyst Derived from a New Three-Dimensional PolyPorphyrin.

Metal-encapsulated nitrogen-doping porous carbonaceous materials (NDPCs) prepared from metalloporphyrin-based covalent organic frameworks (MP-COFs) have become very promising candidates for highly effective oxygen reduction electrocatalysts. To enhance the ORR performance and durability of these NDPCs in novel energy conversion and storage devices, we develop a new type of metal-encapsulated NDPCs (HBY-COF-900) composed of FeN4 active sites by introduction of metalloporphyrin into porous COFs. Comparable to the benchmark 20% Pt/C, HBY-COF-900 in acidic solutions exhibits higher oxygen reduction electrocatalytic activity, long-term durability, and good CO tolerance. These properties can be attributed to a synergistic effect of FeN4 active sites, high graphitization, and porous structure. This work opens an avenue for the development of metal-encapsulated NDPCs from three-dimensional polyporphyrin prepared by one-step polymerization.

A novel biosensor for Escherichia coli O157:H7 based on fluorescein-releasable biolabels.

New techniques are required for the rapid and sensitive detection of Escherichia coli O157:H7 (E. coli O157:H7), a pathogenic bacterium responsible for serious and sometimes life-threatening diseases in humans. In this study, we developed a highly sensitive and efficient biosensor for the quantitative detection of E. coli O157:H7 by integrating fluorescein-releasable biolabels with a magnetism-separable probe. Hollow silica nanospheres with a diameter of approximately 350 nm were synthesized, enriched with fluorescein, and surface-protected with macromolecule layers of poly (acrylic acid) and poly (dimethyldiallylammonium chloride). These fluorescein-enriched hollow silica nanospheres were characterized using scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. They were further functionalized as immune labels of E. coli O157:H7 for a sandwich-type immune reaction between this bacterium and magnetic nanoparticles (Fe3O4@SiO2). Next, the E. coli O157:H7 cells were captured, magnetically separated, and quantified based on the fluorescence intensity of the fluorescein released from the biolabels of the fluorescein-enriched hollow silica nanospheres. This analytic process can be completed within 75 min, and the biosensor showed a linear relationship ranging from 4 to 4.0 × 10(8)cfu/mL with a detection limit of 3 cfu/mL. These results show that the developed fluorescent sensor has excellent specificity, and good reproducibility and stability. This study used real spiked samples for detection, indicating that this technique has a wide range of potential applications and may be readily adapted for detecting other pathogens.

Fluorescent Sulfur-Tagged Europium(III) Coordination Polymers for Monitoring Reactive Oxygen Species.

Oxidative stress caused by reactive oxygen species (ROS) is harmful to biological systems and implicated in various diseases. A variety of selective fluorescent probes have been developed for detecting ROS to uncover their biological functions. Generally, the preparation of the fluorescent probes usually undergoes multiple synthetic steps, and the successful fluorescent sensing usually relies on trial-and-error tests. Herein we present a simple way to prepare fluorescent ROS probes that can be used both in biological and environmental systems. The fluorescent europium(III) coordination polymers (CPs) are prepared by simply mixing the precursors [2,2'-thiodiacetic acid and Eu(NO3)3·6H2O] in ethanol. Interestingly, with the increase of reaction temperature, the product undergoes a morphological transformation from microcrystal to nanoparticle while the structure and fluorescent properties retain. The fluorescence of the sulfur-tagged europium(III) CPs can be selectively quenched by ROS, and thus, sensitive and selective monitoring of ROS in aerosols by the microcrystals and in live cells by the nanoparticles has been achieved. The results reveal that the sulfur-tagged europium(III) CPs provide a novel sensor for imaging ROS in biological and environmental systems.

Porous coordination polymers of transition metal sulfides with PtS topology built on a semirigid tetrahedral linker.

Four novel porous metal sulfide coordination polymers, [M(tpom)S(x)(SH)(y)] x z(H(2)O) (metal-sulfide frameworks, denoted MSF-n, n = 1, Cd; 2, Mn; 3, Fe; 4, Co; x = 0, y = 2 for 1, 2, and 4 and x = 0.54, y = 1.46 for 3), were solvothermally prepared by using a quadridentate linker, tetrakis(4-pyridyloxymethylene)methane (tpom), in the presence of organic sulfur compound under an acidic conditions. MSF-n (n = 1-4) is isostructural and built upon the tetrahedral tpom linker and square planar MS(x)(SH)(y) unit, which form a binodal 4,4-connected porous framework with a 2-fold interpenetrated 4(2)8(4)-pts net. With rectangular pore channels of about 5 x 6 A(2) (interatomic distances between the nearest protruding H atoms across) running along both the crystallographic a and b directions, MSF-n possesses permanent porosity with a BET surface area of 575, 622, 617, and 767 m(2)/g for MSF-1, -2, -3, and -4, respectively, as estimated from N(2) adsorption measurements. MSF-n (n = 1-4) has hydrogen storage capacities of 1.03, 1.37, 1.29, and 1.58 wt % at 77 K and 1 atm, respectively, each corresponding to 2.0 H(2) molecules per unit cell. In addition, MSF-n (n = 1-4) can adsorb 24.1, 25.0, 21.6, and 24.1 wt % of carbon dioxide and 6.0, 6.1, 5.6, and 6.4 wt % of methane, respectively, at room temperature and 20 atm.

Two unprecedented NLO-active coordination polymers constructed by a semi-rigid tetrahedral linker.

The assemblies of tetrahedral linker tetrakis[4-(carboxyphenyl)oxamethyl]methane acid (H(4)L) with ZnCl(2) and CdBr(2) yield two noncentrosymmetric, NLO-active coordination polymers [Zn(4)(L(2))(H(2)O)(3)(DMA)].2H(2)O (1) and [Cd(2)L(DMA)(2)(H(2)O)(2)] (2), respectively. 1 has an unprecedented 2-fold interpenetrating sxa topology with ferroelectric properties, while 2 has a 7-fold interpenetrating dia network.