Simple synthesis of peanut shell-like MoCoFe-HO@CoMo-LDH for efficient alkaline oxygen evolution reaction

Due to the depletion of fossil energy on earth, it is crucial to develop resource rich and efficient non-precious metal electrocatalysts for oxygen evolution reaction (OER). Herein, we synthesized an efficient and economical electrocatalyst using a simple self-assembly strategy. Firstly, rod-shaped MIL-88A was synthesized by hydrothermal method. Then, the surface of MIL-88A was functionalized and encapsulated in zeolitic imidazolate framework-67 (ZIF-67) by hydrothermal method. The combination of MIL-88A and ZIF-67 resulted in a slight ion-exchange reaction between Co2+ and the surface of MIL-88A to generate CoFe-LDH@ZIF-67 core-shell structure. Afterwards, in the presence of Mo6+, ZIF-67 was converted into CoMo-nanocages through ion-exchange reactions, forming a core-shell structure of MoCoFe hydr (oxy) oxide@CoMo-LDH (MoCoFe-HO@CoMo-LDH). Due to the advantages of core-shell structure and composition, this material exhibits excellent OER characteristics, with a small Tafel slope (45.11 mV dec-1) and low overpotential (324 mV) at 10 mA cm-2. It exhibits good stability in alkaline media. This research work provides a novel approach for the development of efficient and economical non-precious metal electrocatalysts.

Natural Polymer Encapsulated Zeolitic Imidazolate Framework-12 Composite toward Electrochemical Sensing of Antitumor Agent

Encapsulation of natural polymer pectin (Pec) into a zeolitic imidazolate framework-12 (ZIF-12) matrix via a simple chemical method toward anticancer agent gallic acid (GA) detection is reported in this work. GA, a natural phenol found in many food sources, has gained attention by its biological effects on the human body, such as an antioxidant and anti-inflammatory. Therefore, it is crucial to accurately and rapidly determine the GA level in humans. The encapsulation of Pec inside the ZIF-12 has been successfully confirmed from the physiochemical studies such as XRD, Raman, FTIR, and XPS spectroscopy along with morphological FESEM, BET, and HRTEM characterization. Under optimized conditions, the Pec@ZIF-12 composite exhibits wide linear range of 20 nM-250 μM with a detection limit of 2.2 nM; also, it showed excellent selectivity, stability, and reproducibility. Furthermore, the real sample analysis of food samples including tea, coffee, grape, and pomegranate samples shows exceptional recovery percentage in an unspiked manner. So far, there is little literature for encapsulating proteins, enzymes, metals, etc., that have been reported; here, we successfully encapsulated a natural polymer Pec inside the ZIF-12 cage. This encapsulation significantly enhanced the composite electrochemical performance, which could be seen from the overall results. All of these strongly suggest that the proposed Pec@ZIF-12 composite could be used for miniaturized device fabrication for the evaluation of GA in both home and industrial applications.

Ultra-Dispersed α-MoC1-x Embedded in a Plum-Like N-Doped Carbon Framework as a Synergistic Adsorption-Electrocatalysis Interlayer for High-Performance Li-S Batteries

The shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) severely hinder the scalable application of lithium-sulfurr (Li-S) batteries. Herein, the highly dispersed α-phase molybdenum carbide nano-crystallites embedded in a porous nitrogen-doped carbon framework (α-MoC1-x @NCF) are developed via a simple metal-organic frameworks (MOFs) assisted strategy and proposed as the multifunctional separator interlayer for Li-S batteries. The inlaid MoC1-x nanocrystals and in situ doped nitrogen atoms provide a strong chemisorption and outstanding electrocatalytic conversion toward LiPSs, whereas the unique plum-like carbon framework with hierarchical porosity enables fast electron/Li+ transfer and can physically suppress LiPSs shuttling. Benefiting from the synergistic trapping-catalyzing effect of the MoC1-x @NCF interlayer toward LiPSs, the assembled Li-S battery achieves high discharge capacities (1588.1 mAh g-1 at 0.1 C), impressive rate capability (655.8 mAh g-1 at 4.0 C) and ultra-stable lifespan (a low capacity decay of 0.059% per cycle over 650 cycles at 1.0 C). Even at an elevated sulfur loading (6.0 mg cm-2 ) and lean electrolyte (E/S is ≈5.8 µL mg-1 ), the battery can still achieve a superb areal capacity of 5.2 mAh cm-2 . This work affords an effective design strategy for the construction of muti-functional interlayer in advanced Li-S batteries.

Surface defect-engineered Fe doping in layered Co-based complex as highly efficient bifunctional electrocatalysts for overall water splitting

The electrocatalytic splitting of water to produce hydrogen is regarded as an efficient and promising strategy but is limited by its large overpotential; thus, a highly efficient electrocatalyst is urgently needed. Mixed metal doping is an important strategy in defect engineering because the heteroatoms can change the intrinsic structure to form defects by affecting the atomic coordination mode and adjusting the electronic structure, which is often accompanied by morphological changes. Herein, two-dimensional layered bimetallic Co-pydc containing axially coordinated water molecules was selected by producing surface defects through Fe doping in Co centers as bifunctional electrocatalysts for OER and HER. The optimized Co0.59Fe0.41-pydc possesses outstanding OER performance with the lowest overpotential of 262 mV to reach j = 10 mA cm-2, and Co0.75Fe0.25-pydc possesses superior HER performance with the lowest overpotential of 96 mV at j = 10 mA cm-2. Furthermore, the overall water splitting device assembled with Co0.59Fe0.41-pydc@NF//Co0.59Fe0.41-pydc@NF affords a current density of 10 mA cm-2 at only 1.687 V. This work emphasizes the surface defects formed by tuning the electronic structure of metal centres accompanied with morphological changes of bimetallic dopants for efficient overall water splitting.

Polyoxometalates@Metal-Organic Frameworks Derived Bimetallic Co/Mo2 C Nanoparticles Embedded in Carbon Nanotube-Interwoven Hierarchically Porous Carbon Polyhedron Composite as a High-Efficiency Electrocatalyst for Al-S Batteries

Al-S battery (ASB) is a promising energy storage device, notable for its safety, crustal abundance, and high theoretical energy density. However, its development faces challenges due to slow reaction kinetics and poor reversibility. The creation of a multifunctional cathode material that can both adsorb polysulfides and accelerate their conversion is key to advancing ASB. Herein, a composite composed of polyoxometalate nanohybridization-derived Mo2 C and N-doped carbon nanotube-interwoven polyhedrons (Co/Mo2 C@NCNHP) is proposed for the first time as an electrochemical catalyst in the sulfur cathode. This composite improves the utilization and conductivity of sulfur within the cathode. DFT calculations and experimental results indicate that Co enables the chemisorption of polysulfides while Mo2 C catalyzes the reduction reaction of long-chain polysulfides. X-ray photoelectron spectroscopy (XPS) and in situ UV analysis reveal the different intermediates of Al polysulfide species in Co/Mo2 C@NCNHP during discharging/charging. As a cathode material for ASB, Co/Mo2 C@NCNHP@S composite can deliver a discharge-charge voltage hysteresis of 0.75 V with a specific capacity of 370 mAh g-1 after 200 cycles at 1A g-1 .

Recent Progress on the Synthesis and Modified Strategies of Zeolitic-Imidazole Framework-67 Towards Electrocatalytic Oxygen Evolution Reaction

As a class of metal-organic framework, the zeolitic-imidazole framework-67 is constructed from bridging cobalt ions and 2-methylimidazole. The high content of abundant active cobalt species, uniform structure, ultrahigh porosity, and large surface area show the potential for multiple catalytic applications, especially electrocatalytic oxygen evolution reaction (OER). The design and synthetic strategies of catalyst-based ZIF-67 that approach the maximized catalytic performance are still challenging in further development. Herein, the current progress strategy on the structural design, synthetic route, and functionalization of electrocatalysts based on ZIF-67 to boost the catalytic performance of OER is reviewed. Besides, the structurally designed catalyst from various fabricated strategies corresponding to enhancing catalytic activity is discussed. The emphasized review for understanding design and synthetic structure with catalytic performance could guide researchers in further developing catalyst-based ZIF-67 for improving the efficient electrocatalytic OER.

Facile synthesis of Ag/ZIF-8@ZIF-67 as an electrochemical sensing platform for sensitive detection of halonitrophenols in drinking water

Halonitrophenols (HNPs) are an emerging type of aromatic disinfection byproduct, with detected concentrations of ∼nmol L-1 in source water and drinking water. Currently, there are no standard methods for identifying HNPs, and most of the reported methods are time-consuming and equipment-dependent. A core-shell metal-organic framework (MOF) based electrochemical sensor (Ag/ZIF-8@ZIF-67) capable of detecting 2,6-dichloro-4-nitrophenol (2,6-DCNP) is reported in this study. The electrochemical sensor obtains the concentration of 2,6-DCNP by detecting the peak current passing through the sensor. In this sensor, Ag nanoparticles (AgNPs) play a key role in electrochemical sensing by reducing nitro groups via electron transfer, and porous structure with a large surface area is offered by ZIF-8@ZIF-67. The cyclic voltammetry (CV) response of Ag/ZIF-8@ZIF-67 was found to be approximately 1.75 times and 2.23 times greater than that of Ag/ZIF-8 and Ag/ZIF-67, respectively, suggesting an ideal synergistic effect of the core-shell structures. The Ag/ZIF-8@ZIF-67 sensor exhibited exceptional sensitivity to 2,6-DCNP, exhibiting a broad linear response range (R2 = 0.992) from 240 nmol L-1 to 288 μmol L-1 and a low detection limit of 20 nmol L-1. Furthermore, the sensor exhibited good anti-interference for isomers and common distractors in water, excellent stability and reproducibility, and high recovery in actual water samples. Our reported sensor gives a novel strategy for sensitive, selective, and in situ detection of 2,6-DCNP in practical analysis.

Advances in the application of metal-organic framework nanozymes in colorimetric sensing of heavy metal ions

Nanozymes, which can be defined as nanomaterials with excellent catalytic function, are well known to the scientific community due to their distinct merits, such as low cost and high stability, which render them preferable to natural enzymes. As porous organic-inorganic coordination materials, metal-organic frameworks (MOFs) possess a large number of active sites and thus can effectively mimic the properties of natural enzymes. Recently, MOF-based nanozymes have also exhibited good application potential for the analysis of heavy metal ions. In comparison to the traditional detection methods for heavy metal ions, nanozyme-based colorimetric sensing permits intuitive visual analysis by using relatively simple instruments, facilitating rapid and simple on-site screening. In this minireview, the preparation of MOF-based nanozymes and the different nanozyme activity types are briefly described, such as peroxidase-like and oxidase-like, and the relevant catalytic mechanisms are elaborated. Based on this, different response mechanisms of MOF-based colorimetric methods to heavy metal ions, such as turn-off, turn-on, and turn-off-on, are discussed. In addition, the colorimetric sensing applications of MOF-based nanozymes for the detection of heavy metal ions are summarized. Finally, the current research status of MOF-based nanozymes and the future development direction are discussed.

Polyoxometalate functionalizing CeO2 hollow nanospheres as enhanced oxidase mimics for ascorbic acid colorimetric sensing

Phosphotungstic acid covered with CeO₂ hollow nanospheres (CeO₂@PTA HNSs) has been successfully prepared by a simple method, serving as highly efficient nanozymes for ascorbic acid (AA) colorimetric sensing. In virtue of the unique hollow nanostructures, oxide defects and synergic effects of CeO₂ and PTA, the proposed CeO₂@PTA HNSs present remarkable intrinsic oxidase-like activity and help capture electrons from 3,3',5,5'-tetramethylbenzidine (TMB). Due to the reducibility of AA, a promising colorimetric sensing platform based on CeO₂@PTA HNSs has been constructed for quantitative analysis of AA. The present colorimetric detection exhibits a low limit of detection, good selectivity and stability, as well as reliability in orange juice and milk. This work provides a simple surface defect engineering to prepare high-performance oxidase mimics in the application of colorimetric biosensing.

Surface Reconstruction of Cobalt-Based Polyoxometalate and CNT Fiber Composite for Efficient Oxygen Evolution Reaction

Polyoxometalates (POMs), as carbon-free metal-oxo-clusters with unique structural properties, are emerging water-splitting electrocatalysts. Herein, we explore the development of cobalt-containing polyoxometalate immobilized over the carbon nanotube fiber (CNTF) (Co4POM@CNTF) towards efficient electrochemical oxygen evolution reaction (OER). CNTF serves as an excellent electron mediator and highly conductive support, while the self-activation of the part of Co4POM through restructuring in basic media generates cobalt oxides and/or hydroxides that serve as catalytic sites for OER. A modified electrode fabricated through the drop-casting method followed by thermal treatment showed higher OER activity and enhanced stability in alkaline media. Furthermore, advanced physical characterization and electrochemical results demonstrate efficient charge transfer kinetics and high OER performance in terms of low overpotential, small Tafel slope, and good stability over an extended reaction time. The significantly high activity and stability achieved can be ascribed to the efficient electron transfer and highly electrochemically active surface area (ECSA) of the self-activated electrocatalyst immobilized over the highly conductive CNTF. This research is expected to pave the way for developing POM-based electrocatalysts for oxygen electrocatalysis.

An inorganic-organic hybrid nanomaterial with a core-shell structure constructed by using Mn-BTC and Ag5[BW12O40] for supercapacitors and photocatalytic dye degradation

Creating inorganic-organic hybrids with polyoxometalates (POMs) and metal-organic frameworks (MOFs) as energy storage and dye-degradation materials remains challenging. Here, a new hybrid nanomaterial Mn-BTC@Ag₅[BW₁₂O₄₀] is synthesized by using Ag₅[BW₁₂O₄₀] and Mn₃(BTC)₂(H₂O)₆ (Mn-BTC, BTC = 1,3,5-benzenetricarboxylic acid) through a plain grinding method. The structure and morphology characterization by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) shows that the synthetic products have core-shell construction. Due to its unique structure wherein the core is Mn-BTC and the shell is Ag₅[BW₁₂O₄₀], it exhibits excellent capacitance performance. In a three-electrode system where nickel foam is a collector, at a current density of 1 A g^-1, its specific capacitance is 198.09 F g^-1; after 5000 cycles, the capacitance retention rate is 94.4%. When the power density is 503.1 W kg^-1, the symmetrical supercapacitor reveals a high energy density which is 10.9 W h kg^-1. At the same time, the capacitance retention is 92.9% after 5000 cycles which showed good cycle stability. The photocatalytic degradation efficiencies of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) dyes exceed 90% after 140 min, and the degradation results remained unchanged after five photocatalytic cycles. The photocatalytic degradation mechanism shows that ˙OH has a major effect. The results show that this research provides a fresh idea for the development of energy storage and dye photocatalytic degradation materials.

The High Electrocatalytic Performance of NiFeSe/CFP for Hydrogen Evolution Reaction Derived from a Prussian Blue Analogue

Non-noble-metal-based chalcogenides are promising candidates for hydrogen evolution reaction (HER) by harnessing the architectural design and the synergistic effect between the elements. Herein, a porous bimetallic selenide (NiFeSe) nanocube deposited on carbon fiber paper (NiFeSe/CFP) was synthesized through a facile selenization reaction based on Prussian blue analogues (PBAs) as precursors. The NiFeSe/CFP exhibited excellent HER activity with an overpotential of just 186 mV for a current density of 10 mA cm−2 in 1.0 M KOH at ambient temperature, similar to most of the state-of-the-art transition metal chalcogenides. The corresponding Tafel slope was calculated to be 52 mV dec−1, indicating fast discharge of the proton during the HER. Furthermore, the catalyst could endure long-term catalytic tests and showed remarkable durability. The enhanced electrocatalytic performance of NiFeSe/CFP is attributed to the unique 3D porous configuration inherited from the PBA templates, enhanced charge transfer occurring at the heterogeneous interface due to the synergistic effect between the bimetallic phases, and the high conductivity improved by the formation of amorphous carbon shells during the selenization. These findings prove that the combination of inexpensive metal–organic framework precursors and hybrid metallic compounds is a feasible way to realize the performance enhancement of non-noble-metal-based chalcogenides towards alkaline HER.

Synergetic Effects of Mixed-Metal Polyoxometalates@Carbon-Based Composites as Electrocatalysts for the Oxygen Reduction and the Oxygen Evolution Reactions

The smart choice of polyoxometalates (POMs) and the design of POM@carbon-based composites are promising tools for producing active electrocatalysts for both the oxygen reduction (ORR) and the oxygen evolution reactions (OER). Hence, herein, we report the preparation, characterization and application of three composites based on doped, multi-walled carbon nanotubes (MWCNT_N6) and three different POMs (Na12[(FeOH2)2Fe2(As2W15O56)2]·54H2O, Na12[(NiOH2)2Ni2(As2W15O56)2]·54H2O and Na14[(FeOH2)2Ni2(As2W15O56)2]·55H2O) as ORR and OER electrocatalysts in alkaline medium (pH = 13). Overall, the three POM@MWCNT_N6 composites showed good ORR performance with onset potentials between 0.80 and 0.81 V vs. RHE and diffusion-limiting current densities ranging from −3.19 to −3.66 mA cm−2. Fe4@MWCNT_N6 and Fe2Ni2@MWCNT_N6 also showed good stability after 12 h (84% and 80% of initial current). The number of electrons transferred per O2 molecule was close to three, suggesting a mixed regime. Moreover, the Fe2Ni2@MWCNT_N6 presented remarkable OER performance with an overpotential of 0.36 V vs. RHE (for j = 10 mA cm−2), a jmax close to 135 mA cm−2 and fast kinetics with a Tafel slope of 45 mV dec−1. More importantly, this electrocatalyst outperformed not only most POM@carbon-based composites reported so far but also the state-of-the-art RuO2 electrocatalyst. Thus, this work represents a step forward towards bifunctional electrocatalysts using less expensive materials.

Critical Review, Recent Updates on Zeolitic Imidazolate Framework-67 (ZIF-67) and Its Derivatives for Electrochemical Water Splitting

Design and construction of low-cost electrocatalysts with high catalytic activity and long-term stability is a challenging task in the field of catalysis. Metal-organic frameworks (MOF) are promising candidates as precursor materials in the development of highly efficient electrocatalysts for energy conversion and storage applications. This review starts with a summary of basic concepts and key evaluation parameters involved in the electrochemical water-splitting reaction. Then, different synthesis approaches reported for the cobalt-based Zeolitic imidazolate framework (ZIF-67) and its derivatives are critically reviewed. Additionally, several strategies employed to enhance the electrocatalytic activity and stability of ZIF-67-based electrocatalysts are discussed in detail. The present review provides a succinct insight into the ZIF-67 and its derivatives (oxides, hydroxides, sulfides, selenides, phosphide, nitrides, telluride, heteroatom/metal-doped carbon, noble metal-supported ZIF-67 derivatives) reported for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting applications. Finally, this review concludes with the associated challenges and the perspectives on developing the best economic, durable electrocatalytic materials.

Polyoxometalate-based metal–organic complexes and their derivatives as electrocatalysts for energy conversion in aqueous systems

The research progress on polyoxometalate-based metal–organic complexes and their derivatives as electrocatalysts in sustainable and clean energy conversion applications in aqueous systems is summarized.

Preparation and characterization of a newly constructed multifunctional Co(ii)–organic framework: proton conduction and adsorption of Congo red in aqueous medium

The efficient adsorption of CR over Co-MOF 1 as well as the pH-dependent proton-conducting mechanism of the composite Co-MOF–Nafion membrane.

A two-dimensional zeolitic imidazolate framework loaded with an acrylate-substituted oxoiron cluster as an efficient electrocatalyst for the oxygen evolution reaction

An acrylate-substituted oxoiron cluster {Fe28} has been loaded with 2D ZIF-L, which exhibits a superior OER performance.

ZIF-67-based catalysts for oxygen evolution reaction

As a new type of crystalline porous material, the imidazole zeolite framework (ZIF) has attracted widespread attention due to its ultra-high surface area, large pore volume, and unique advantage of easy functionalization. Developing different methods to control the shape and composition of ZIF is very important for its practical application as catalyst. In recent years, nano-ZIF has been considered an electrode material with excellent oxygen evolution reaction (OER) performance, which provides a new way to research electrolyzed water. This review focuses on the morphological engineering of the original ZIF-67 and its derivatives (core-shell, hollow, and array structures) through doping (cation doping, anion doping, and co-doping), derivative composition engineering (metal oxide, phosphide, sulfide, selenide, and telluride), and the corresponding single-atom catalysis. Besides, combined with DFT calculations, it emphasizes the in-depth understanding of actual active sites and provides insights into the internal mechanism of enhancing the OER and proposes the challenges and prospects of ZIF-67 based electrocatalysts. We summarize the application of ZIF-67 and its derivatives in the OER for the first time, which has significantly guided research in this field.

Temperature-Controlled Structural Variations of Meticulous Fibrous Networks of NiFe-Polymeric Zeolite Imidazolate Frameworks for Enhanced Performance in Electrocatalytic Water-Splitting Reactions

Developing non-noble, earth-ample, and stable electrocatalysts are highly anticipated in oxygen-evolution reaction (OER) and hydrogen-evolution reaction (HER) at unique pH conditions. Herein, we have synthesized bimetallic (nickel and iron) zeolite imidazolate framework (ZIF)-based nanofibrous materials via a simple electrospinning (ES) process. The structural stability of the fibrous material is subjected to various calcination conditions. We have elaborated the structural importance of the one-dimensional (1D) fibrous materials in electrocatalytic water-splitting reactions. As a result, NiFe-ZIF-NFs (Nanofibers)-RT (Room Temperature) have delivered a small overpotential of 241 mV at 10 mA cm^-2 current density in OER and 290 mV at a fixed current density of 50 mA cm^-2 in HER at two different pH conditions with 1 M KOH and 0.5 M H₂SO₄, respectively. Furthermore, it exposes the actual surface area of 27.270 m² g^-1 and a high electrochemical active surface area (ECSA) of 50 μF in OER and 55 μF in HER, which is responsible for the electrochemical performance with better stability. This exceptional activity of the materials is mainly attributed to the structural dependency of the fibrous network through the polymeric architecture.

When Conductive MOFs Meet MnO2: High Electrochemical Energy Storage Performance in an Aqueous Asymmetric Supercapacitor

Metal organic frameworks (MOFs) have been widely researched and applied in many fields. However, the poor electrical conductivity of many traditional MOFs greatly limits their application in electrochemistry, especially in energy storage. Benefited from the full charge delocalization in the atomical plane, conductive MOFs (c-MOFs) exhibit good electrochemical performance. Besides, unlike graphene, c-MOFs are provided with 1D cylindrical channels, which can facilitate the ion transport and enable high ion conductivity. Transition-metal oxides (TMOs) are promising materials with good electrochemical energy storage performance due to their excellent oxidation-reduction activity. When composited with TMOs, the c-MOFs can significantly improve the capacitance and rate performance. In this work, for the first time, we designed serial MnO₂@Ni-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanoarrays with different lengths and explored how the lengths influence the electrochemical energy storage performance. By taking advantage of the high redox activity of MnO₂ and the excellent electron and ion conductivity in Ni-HHTP, when assembled as the positive electrode material in an aqueous asymmetric supercapacitor, the device displays high energy density, outstanding rate performance, and superior cycle stability. We believe that the results of this work would provide a good prospect for developing other c-MOF composites as a potential class of electrode materials in energy storage and conversion.

A robust CRISPR-Cas12a biosensor coated with metal-organic framework

Metal-organic frameworks (MOFs) are proposed to protect a CRISPR-associated enzyme/RNA complex from harsh environments, while the complex can be quickly released from MOFs with high efficiency. Therefore, the application of CRISPR-powered biosensing can be more feasible.

Onion-Ring-like Carbon and Nitrogen from ZIF-8 on TiO2/Fe2O3 Nanostructure for Overall Electrochemical Water Splitting

The carbon and nitrogen derived from ZIF-8 embedded in TiO₂/Fe₂O₃ (i.e., C,N-ZIF/TiFe) nanostructures exhibit superior electrocatalytic performance toward oxygen evolution reactions (OER), hydrogen evolution reactions (HER), and overall H₂O splitting. The results showed that the C,N-ZIF/TiFe nanostructure was the best catalyst in comparison to ZIF/TiFe and TiFe nanostructures toward HER and OER. These results revealed that combining the highly active carbon and nitrogen from ZIF-8 with a TiO₂/Fe₂O₃ semiconductor enriched the overall H₂O splitting. A possible OER mechanism is attributed to some groups that support the surface active site of the catalyst and adsorbent intermediate species. Finally, this inexpensive electrocatalyst was synthesized without noble metals and showed superior electrocatalytic activity and great stability with the potential to achieve ground-breaking and novel applications in fuel cells.

Assembly of polyoxometalate-thiacalix[4]arene-based inorganic-organic hybrids as efficient catalytic oxidation desulfurization catalysts

Self-assembly of polyoxometalates, Ni(ii)/Ag(i) cations and tetra-[5-(mercapto)-1-methyltetrazole]-thiacalix[4]arene (L) yielded three inorganic-organic hybrids, namely, [Ni₃L₂(CH₃OH)₆(H₂O)₄][PMo₁₂O₄₀]₂·3CH₃OH·2H₂O (1), [Ni₃L₂(CH₃OH)₆(H₂O)₄][PW₁₂O₄₀]₂·3CH₃OH·2H₂O (2) and [Ag₃L(PMo₁₂O₄₀)] (3). In hybrids (1) and (2), Ni(ii) cations are linked by L ligands to produce layered frameworks, and H bonds among the [PMo₁₂O₄₀]^3-/[PW₁₂O₄₀]^3- anions and L ligands lengthen the structures to form 3D supramolecular architectures. Hybrid (3) exhibits a 3D architecture, of which Ag(i) cations not only coordinated with the N and O atoms of L ligands and [PMo₁₂O₄₀]^3- anions simultaneously, but also connected each other by Ag-Ag interactions. It is worth mentioning that 1 and 3 as recyclable catalysts show excellent heterogeneous catalytic activity in oxidation desulfurization reactions.

Ten polytorsional-amide-induced helical-based coordination polymers with difunctional electrochemical activities

Ten polytorsional-naphthalene-amide-based CPs constructed from different carboxylates and metal ions were obtained and exhibited difunctional electrochemical activities.

Assembly of ZIF-67 nanoparticles and in situ grown Cu(OH)2 nanowires serves as an effective electrocatalyst for oxygen evolution

Due to the slow kinetics of oxygen evolution at the anode, the efficiency of electrocatalytic water decomposition is critically reduced, and its large-scale application is severely restricted. Therefore, it is urgent to develop electrocatalysts with excellent performance and stability to accelerate the oxygen evolution reaction (OER) reaction kinetics. Herein, a self-supporting binder-free electrocatalyst was successfully prepared using in situ grown Cu(OH)2 nanowires on CF as the carrier to grow ZIF-67 via a room temperature immersion method. The combination of Cu(OH)2 nanowires and the unique structure of ZIF-67 forms a three-dimensional nanostructured catalyst, in which the unique structure and the existence of synergy may contribute to a larger electrochemical active surface area, expose more electrochemically active sites, adjust the electronic structure, and accelerate the rate of electron transfer, thus greatly improving the electrocatalytic activity and durability for OER. The as-prepared Cu(OH)2@ZIF-67/CF exhibited excellent OER performance under alkaline conditions and required overpotentials of 205 mV and 276 mV to drive current densities of 10 mA cm-2 and 100 mA cm-2, respectively, with a small Tafel slope of 70.5 mV dec-1 for OER. The stability test of Cu(OH)2@ZIF-67/CF at the current density of 10 mA cm-2 displayed excellent stability for 22 h. This study provides a feasible strategy for the rapid preparation of low-cost and efficient electrocatalysts in alkaline media.

POM-Based MOF-Derived Co3O4/CoMoO4 Nanohybrids as Anodes for High-Performance Lithium-Ion Batteries

Polyoxometalate (POM)-based metal-organic framework (MOF)-derived Co₃O₄/CoMoO₄ nanohybrids were successfully fabricated by a facile solvothermal method combined with a calcination process, in which a Co-based MOF, that is, ZIF-67 acts as a template while a Keggin-type POM (H₃PMo₁₂O₄₀) serves as a compositional modulator. The materials were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) mapping, and electrochemical measurements. When the Co₃O₄/CoMoO₄ nanohybrids were applied as anode materials for lithium-ion batteries (LIBs), they display large lithium storage capacity (around 900 mAh g^-1 at 0.1 A g^-1) and high cycling stability, and they can also exhibit good rate performances. This work might shed some light on the POM-based MOF host-guest synthesis strategy for the preparation of polymetallic oxides for enhanced electrochemical energy storage and further applications.

An electrochemical aptasensor-based CoxP-decorated porous carbon microspheres and AuNRs labelled methylene blue as signal labels for the sensitive detection of PCB77

In this work, a simple, specific and ultra-sensitive electrochemical aptasensor was successfully developed based on a novel signal reduction strategy for the detection of polychlorinated biphenyls (PCB77). This aptasensor was prepared by the electrodeposition of gold nanoparticles (AuNPs) on an Au electrode (AuE) modified with cobalt phosphide (Co_xP, a mixture of CoP and Co₂P) decorated porous carbon microspheres. In this study, the thiolated single-complementary DNA (cDNA) was immobilized on the surface of the modified electrode via the Au-S bond. Subsequently, the gold nanorod@methylene blue connection aptamer (AuNRs@MB-Apt) signal labels were immobilized onto the modified electrode through the principle of complementary base pairing. Further, the aptamer preferentially binds to PCB77, decreasing the amount of AuNR@MB-Apt. The DPV current response was related to the PCB77 concentration. Under the optimized experimental conditions, a low detection limit of 5.9 × 10^-2 ng L^-1 and a wide linear range of 1 × 10^-11 mg mL^-1 to 1 × 10^-4 mg mL^-1 (S/N = 3) for PCB77 were achieved. Moreover, the proposed aptasensor offered high selectivity, stability and reproducibility, indicating the broad potential application in environmental monitoring.

Anchoring ZIF-67 particles on amidoximerized polyacrylonitrile fibers for radionuclide sequestration in wastewater and seawater

Capturing uranium (U(VI)) ions from wastewater and seawater is highly attractive for the environment and clean energy with the increasing deficiency of land sources. Howbeit, the massive volume of water and the ultralow concentration of U(VI) pose a substantial challenge to the industrial application. Accordingly, we have synthesized a novel organic-inorganic hybrid adsorbent through in-situ growing MOF particles on electrospun polyacrylonitrile fibers (PAN) followed by modifing with amidoxime groups to form amidoximed PAN/ZIF-67 (AOPAN/ZIF) hybrid fibers. In such fibers, the N atoms from imidazole and amidoxime can improve the adsorption performance synergistically in a wide pH range, which is favorable for capturing U(VI) under nuclear wastewater and seawater. As a result, the AOPAN/ZIF fibers exhibit high adsorption amount of 498.4 mg g^-1 in U(VI) contaminated aqueous solution at pH 4. Furthermore, the adsorption amount of U(VI) reached 2.03 mg g^-1 in natural seawater after 36 d, which implies that the AOPAN/ZIF fibers may promote the development of U(VI) recovery.