Surface Of ZIF-8 Research Articles

Efficient ibuprofen removal using enzymatic activated ZIF-8-PVDF membranes

This study investigated the development of poly(vinylidene fluoride) (PVDF) hybrid ultrafiltration membranes, where ZIF-8 nanocrystals are synthesized in situ within the membrane pores. These ZIF-8 embedded membranes are specifically designed for the treatment of emerging pollutants, such as ibuprofen. The optimized membrane, characterized by a higher concentration of ZIF-8 and greater surface coverage, exhibited significantly enhanced performance and improved properties, including increased hydrophobicity and mechanical strength. By increasing the zinc concentration from 0.2 to 0.3 M during the preparation of the ZIF-8 coated membrane, hydrophobicity was enhanced, as indicated by an increase in the contact angle from 60.3° to 87.2°, along with improved porosity from 41.3% to 60.5%. Further performance enhancements were achieved by encapsulating enzymes, specifically laccase and peroxidase, within the ZIF-8 coated membrane. A comparison of ibuprofen removal by these enzymes showed that peroxidase was slightly more effective, reaching a maximum removal efficiency of approximately 45% within 2 h. The biocatalytic membranes demonstrated a high stability and reusability, underscoring their potential for efficient ibuprofen removal. These findings highlight the efficacy of ZIF-8-coated PVDF membranes as advanced tools for water purification, offering significant improvements in both purification efficiency and membrane stability.

Construction of Methotrexate-Loaded Bi2S3 Coated with Fe/Mn-Bimetallic Doped ZIF-8 Nanocomposites for Cancer Treatment Through the Synergistic Effects of Photothermal/Chemodynamic/Chemotherapy.

A combination of therapeutic modalities in a single nanostructure is crucial for a successful cancer treatment. Synergistic photothermal therapy (PTT) can enhance the effects of chemodynamic therapy (CDT) and chemotherapy, which could intensify the therapeutic efficacy to induce cancer cell apoptosis. In this study, Fe and Mn on a zeolitic imidazolate framework (ZIF-8) (Fe/Mn-ZIF-8; FMZ) were synthesized through ion deposition. Furthermore, bismuth sulfide nanorods (Bi2S3 NRs; BS NRs) were synthesized via a hydrothermal process and coated onto FMZ to generate the core-shell structure of the Bi2S3@FMZ nanoparticles (B@FMZ). Next, methotrexate (MTX) was loaded effectively onto the porous surface of ZIF-8 to form the B@FMZ/MTX nanoparticles. The Fenton-like reaction catalyzes Fe2+/Mn2+ ions by decomposing H2O2 in the tumor microenvironment, resulting in the formation of toxic hydroxyl radicals (·OH), which promotes the CDT effect of killing cancer cells. Furthermore, under 808 nm laser irradiation, these B@FMZ nanoparticles showed a strong PTT effect, owing to the presence of intense BS NRs as a photothermal agent. The B@FMZ nanoparticles exhibited a prominent drug release efficiency of 87.25% at pH 5.5 under near-infrared laser irradiation due to the PTT effect can promote the drug delivery performance. The B@FMZ nanoparticles were subjected to dual-modal imaging, guided magnetic resonance imaging, and X-ray computed tomography imaging. Both in vitro and in vivo results suggested that the B@FMZ/MTX nanoparticles exhibited enhanced antitumor effects through the combined therapeutic effects of PTT, CDT, and chemotherapy. Therefore, these nanoparticles exhibit good biocompatibility and are promising candidates for cancer treatment.

Development of a heterogeneous MOF-on-MOF photo-Fenton catalyst for highly efficient tetracycline degradation across a broad pH spectrum

The utilization of MOF-on-MOF heterojunction materials has demonstrated exceptional functional scalability; however, their application in the realm of photocatalytic degradation remains relatively limited. This study focuses on the synthesis of a MOF-on-MOF heterojunction involving the growth of Prussian blue (PB) onto the surface of ZIF-8, with ZIF-8 serving as a seed. The optimized MOF-on-MOF heterostructure catalyst, denoted as PB@ZIF-8, exhibited a degradation efficiency exceeding 98 % across the pH range of 4.0–10 in the Fenton system under sunlight irradiation. Notably, the reaction rate constant in the PB@ZIF-8/H2O2/Sun system was 0.029 min−1, which is 2.43 and 2.36 times higher than that of pure PB and ZIF-8. The superior performance of PB@ZIF-8 was attributed to the synergistic effect of PB and ZIF-8 in the MOF-on-MOF composite, which played a pivotal role in the tetracycline degradation process by enhancing light absorption and facilitating the separation of carriers. Furthermore, the PB@ZIF-8 catalyst exhibited exceptional stability, allowing for 5 cycles of recycling while consistently maintaining a degradation efficiency exceeding 97 %. This research not only expands the possibilities for architecting MOF-on-MOF structures but also contributes to the development of heterojunction materials for the removal of emerging pollutants from wastewater.

Efficient Low-Pressure CO2 capture via ZIF-8 modified by deep eutectic solvents

To enhance CO2 sorption efficiency under low-pressure conditions and effectively compete with N2 sorption in flue gas, modifications are implemented aimed at improving the adsorption capacity and selectivity of ZIF-8, renowned for their robust stability. Deep eutectic solvent (DES) comprising tetraethylammonium chloride (TEAC), tetrapropylammonium chloride (TPAC), and tetrabutylammonium bromide (TBAB) as hydrogen-bond acceptors, along with ethanolamine (MEA) as the hydrogen-bond donor, were meticulously prepared for this purpose. ZIF-8 underwent modification through DES loading, resulting in the distinctive emergence of a “core-membrane” structure. Characterization revealed that the DES effectively adhered to the surface of ZIF-8 in a membrane-like structure, without altering the chemical structure or pore size of ZIF-8. The most significant enhancement in sorption capacity was observed with TPAC&MEA modification. Considering the presence of N2 partial pressure in the flue gas, at 0.05 and 1 bar, the CO2 adsorption capacities reached 1.92 and 3.03 mmol g−1, respectively, increasing 71.11 and 4.00 times compared to pristine ZIF-8. The ZIF-8 exhibited a CO2/N2 separation coefficient of 72.77, which increased to a maximum of 997.50 after DES modification. Additionally, the modified material demonstrated exceptional cyclic and thermal stability during testing. This study significantly elevates the CO2 adsorption capacity and selectivity of solid materials within the low-pressure range, providing pivotal support for CO2 capture and decarbonization efforts.

Creation of intrinsic defects on ZIF-8 particles to facilitate electrochemical reduction of CO2 over Fe single-atom catalyst

The fabrication of various defects on the surface of metal single-atom catalysts can improve their electrochemical CO2 reduction reaction (CO2RR) ability, and the current mainstream research focuses on the defect modification of heteroatom doping, while there are fewer studies on intrinsic defects on carbon substrates. Herein, a series of catalysts with both Fe-N4 sites and intrinsic defects were synthesized on the ZIF-8 surface by pyrolytic etching at a suitable temperature under ammonia atmosphere. Electrochemical tests in an H-cell showed that the catalyst achieved CO Faradaic efficiency (FECO) of 96.9 % and CO partial current density (JCO) of 9.088 mA cm−2 at −0.6 V. Through further studies, we introduced a “585” ring structure to describe these intrinsic defects and found that these intrinsic defects on the carbon-based surface can act as active sites to promote CO2RR along with the Fe-N4 sites. This work provides a reference for the study of intrinsic defect-modified single atomic materials.

Multiple synergistic antibacterial melamine-impregnated paper based on nano Ag-doped ZIF-8

Melamine-impregnated paper, a decorative material in furniture and interior design, could potentially impede the spread of indoor bacteria if it possesses antibacterial properties. Here, nano Ag-doped ZIF-8 (Ag@ZIF-8) was synthesized using ion exchange and in-situ chemical reduction strategies, followed by incorporating it into melamine-impregnated paper. The ion exchange mechanism of Zn2+ and Ag+ during ion exchange reactions was investigated. The structure of Ag@ZIF-8 was well-defined, with Ag nanoparticles evenly distributed on the surface of ZIF-8. Ag@ZIF-8 showed good thermal stability at 400 °C, meeting the requirements for the hot-pressing process of the melamine-impregnated paper. Ag@ZIF-8 exhibited enhanced ROS generation under visible light compare to ZIF-8, which was attributed to its reinforced light absorption and charge carrier separation facilitated by the localized surface plasmon resonance (LSPR) effect. The antibacterial activity of Ag@ZIF-8 was better than ZIF-8, owing to the multiple-synergistic antibacterial mechanisms of the ion release and ROS generation. Specifically, the 10-Ag@ZIF-8 exhibited MIC of 128 μg/mL and 64 μg/mL against E. coli and S. aureus, respectively. The signal intensity of •O2 − induced by 10-Ag@ZIF-8 was 4.38 times higher than that of ZIF-8. As the addition of Ag@ZIF-8 increased, the antibacterial performance of melamine-impregnated paper improved. Considering the antibacterial property and economy of melamine-impregnated paper, 0.20 wt% was the optimal amount for 10-Ag@ZIF-8 decorated blockboard. This study proposes a novel approach for synthesizing MOF-based melamine-impregnated paper with antibacterial properties, aiming to reduce bacterial spread, minimize disease risks, and contribute to lowering overall healthcare costs.

Preparation of Ni, Co doped hollow carbon nanocage from core-shell structure ZIF-8@ZIF-67 for nitrobenzene monitoring

Herein, we employed a Ni, Co duplex metal-doped hollow carbon nanocage derived from the core-shell Zeolite imidazole framework-8 (Zn)@Zeolite imidazole framework-67 (Co) (ZIF-8@ZIF-67) for the sensitive electrochemical detection of nitrobenzene (NB). The precursor was created by coating ZIF-67 on the surface of ZIF-8 through the epitaxial growth method, followed by Ni doping. Subsequent pyrolysis resulted in the formation of a Ni, Co duplex metal-doped hollow carbon nanocage. Characterization of the nanocomposite confirmed the unique hollow and porous structure of NiCo/C, maintaining a dodecahedral morphology with a uniform distribution of carbon and transition metal nanoparticles. The NiCo/C-modified electrode exhibits a wide linear dynamic range (0.05–11.22 μM and 11.22–230.06 μM), a lower limit of detection (0.14 μM), superior stability and selectivity for the detection of NB. Moreover, it shows appropriate practicality toward detecting NB in natural water samples.

Construction of MnO2@ZIF-8 core-shell nanocomposites for efficient removal of Sr2+ from aqueous solution

Novel MnO2@ZIF-8 nanocomposites were synthesized for efficient adsorptive removal of Sr2+ from aqueous solution. ZIF-8 nanoparticles with controlled morphology and size were first synthesized by using amino acids to modulate the crystal nucleation and growth. Then, a layer of MnO2 nanoparticles were deposited on ZIF-8 surface by using the adsorbed amino acid molecules as binding sites to mediate MnO2 mineralization and by adjusting the reactive KMnO4 concentration to control the size and surface density of the MnO2 nanoparticles. The as-prepared MnO2@ZIF-8 nanocomposites showed a core-shell structure and displayed superior performance in Sr2+ adsorption and removal from aqueous solution. The adsorption process can be described well by the pseudo-second-order equation. The adsorption isotherm accords well with the Langmuir model and the maximum adsorption capacity can reach 65.7 mg/g. The study paves a new way to develop novel inorganic nanocomposites as highly efficient and potential adsorbents for the treatment of radionuclide-containing wastewater.

Adsorption enhances CH4 transport-driven hydrate formation in size-varied ZIF-8: Micro-mechanism for CH4 storage by adsorption-hydration hybrid technology

The adsorption-hydration hybrid technology holds significant potential for future CH4 storage applications. However, the transport of CH4/H2O and the mechanisms governing hydrate formation within metal-organic framework (MOF) systems remain unclear. In this study, the mechanism of CH4 adsorption, transport, and hydrate formation within ZIF-8 pores of different sizes was delineated utilizing the magnetic resonance imaging (MRI) technique. Primarily, CH4 undergoes physisorption within the inner cavity of ZIF-8, facilitating diffusion through the pores, which preferentially accumulate in larger pore spaces. Due to favorable interactions between CH4 and pre-absorbed water on the ZIF-8 surface, ZIF-8–01 and ZIF-8–02 preferentially facilitate substantial hydrate formation within larger pore spaces. The continuous hydrate growth depletes CH4 in the pore space, enabling two-way migration of adsorbed CH4 to support ongoing hydrate formation. This limited availability of adsorption sites within ZIF-8 induces the diffusion of surrounding CH4 into smaller pore spaces, facilitating the conversion of bound water. The size of the particles considerably influences the transport of physically adsorbed CH4 and impacts hydrate formation. Similar patterns are observed in the adsorption mass transfer coefficients of ZIF-8–01 and ZIF-8–02, which range from 0.0038 to 0.0044 and 0.0031 to 0.0124, respectively. The presence of more adsorption vacancies in the early stage leads to rapid diffusion adsorption of CH4 owing to strong adsorption effects. As adsorption within ZIF-8 pore cavities approaches saturation, increased water transport elevates internal gas-liquid two-phase resistance, slowing the kinetics of late-stage CH4 adsorption. At 6 MPa, CH4 with a larger particle size preferentially overcomes the gas-liquid energy barrier, expediting transport and promoting hydrate formation. Furthermore, the optimal particle sizes of ZIF-8 substantially influence physisorption and significantly improve the kinetics of hydrate formation.

Unraveling the orientation of an enzyme adsorbed onto a metal-organic framework.

Bio-conversion of lignocellulosic biomass to bioethanol fuel is a highly desirable yet challenging objective because of the low catalytic activity and high cost of β-glucosidase (BGL). Recently, ZIF-8, an emerging organic porous material, has been proposed as a promising candidate for enzyme immobilization to improve associated activity and stability. However, the underlying interaction mechanism of binding BGL on the ZIF-8 surface is yet to be clarified. Here, the adsorption of BGL onto ZIF-8 is explored for the first time by molecular dynamics simulations. The results show that BGL adsorbs on the ZIF-8 surface with a "back-on" orientation. The adsorption free energy analysis shows that the adsorption process is enthalpy driven. In addition, the electrostatic interaction between negatively charged residues and Zn2+ on the surface of ZIF-8 is found to play a decisive role in surface binding, which accounts for 98% of the total interaction energy. The secondary structure of BGL is not affected despite the strong adsorption, suggesting the good biocompatibility of ZIF-8. This study not only provides a reliable theoretical insight into understanding the interaction mechanism between BGL and ZIF-8, but also helps the rational design of ZIF-8-based materials for bio-related applications.

Synthesis of Os@ZIF-8 nanocomposites with enhanced peroxidase-like activity for detection of Hg2.

Metal organic framework (MOF)-derived nanostructures display remarkable characteristics and have broad application potential. Os@ZIF-8 nanocomposites were prepared by a depositional method. The Os nanoparticles distributed on the surface of ZIF-8. The nanocomposites displayed enhanced peroxidase-like activity with smaller Km for both 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 compared to Os NPs due to the confinement effect and large surface area that ZIF-8 provided. From the average reaction rate constants obtained from three different temperatures, the activation energy values were determined. The kinetic data indicated that the Os@ZIF-8 NCs are catalytically more active than Os NPs. In addition, quantitative measurement of Hg2+ was performed based on the formation of Os-Hg alloy. Os@ZIF-8 NCs had a wide detection range between 0 μM and 71.43 μM for Hg2+ with a limit of detection (LOD) of 2.29 μM. Using a MOF with a large surface area to load Os nanoparticles to achieve enhanced nanozyme activity is the novelty of this work.

CO2 adsorption mechanisms at the ZIF-8 interface in a Type 3 porous liquid

Porous liquids (PLs) are an attractive material for gas separation and carbon sequestration due to their permanent internal porosity and high adsorption capacity. PLs that contain zeolitic imidazole frameworks (ZIFs), such as ZIF-8, form PLs through exclusion of aqueous solvents from the framework pore due to its hydrophobicity. The gas adsorption sites in ZIF-8 based PLs are historically unknown; gas molecules could be captured in the ZIF-8 pore or adsorb at the ZIF-8 interface. To address this question, ab initio molecular dynamics was used to predict CO2 binding sites in a PL composed of a ZIF-8 particle solvated in a water, ethylene glycol, and 2-methylimidazole solvent system. The results show that CO2 energetically prefers to reside inside the ZIF-8 pore aperture due to strong van der Waals interactions with the terminal imidazoles. However, the CO2 binding site can be blocked by larger solvent molecules that have greater adsorption interactions. CO2 molecules were unable to diffuse into the ZIF-8 pore, with CO2 adsorption occurring due to binding with the ZIF-8 surface. Therefore, future design of ZIF-based PLs for enhanced CO2 adsorption should be based on the strength of gas binding at the solvated particle surface.

Core-Shell ZIF-8@ZIF-67-Derived Cobalt Nanoparticle-Embedded Nanocage Electrocatalyst with Excellent Oxygen Reduction Performance for Zn-Air Batteries.

Metal-nitrogen-carbon (M-N-C) catalysts obtained from zeolitic imidazolate frameworks (ZIFs) have great potential in the oxygen reduction reaction (ORR). Herein, based on the same three-dimensional (3D) topological structure of ZIF-67 and ZIF-8, ZIF-67 is grown on the ZIF-8 surface by the epitaxial growth method, and ZIF-8 is used as a sacrificial template to obtain a Co-embedded layered porous carbon nanocage (CoPCN) electrocatalyst. Meanwhile, the self-sacrificing template effectively improves the specific surface area of the porous structure and reduces the depletion of active sites. The CoPCN shows a high half-wave potential of 0.885 V and superior stability as well as excellent methanol resistance. Theoretical calculations demonstrate that the Co-N1-C2 sites of CoPCN effectively reduce the energy barrier of ORR. In addition, a zinc-air battery (ZAB) based on the CoPCN exhibits excellent peak power density (90 mW cm-2) and superior cycle performance. This work presents a novel idea in the design of ZIF precursor systems to synthesize efficient ORR catalysts.

Highly selective gas sensors for formaldehyde detection based on ZnO@ZIF‑8 core-shell heterostructures

Formaldehyde is a hazardous volatile organic pollutant commonly found indoors, making selective and accurate detection of formaldehyde crucial. To achieve this, ZnO@ZIF-8 core-shell heterostructures were fabricated using the sacrificial template method, where the 3D ZnO flower-like structures served as the core material. This innovative approach utilizing the ZIF-8 shell as a “selective gas filter” offers a novel pathway for enhancing the selectivity of formaldehyde sensors. Subsequent investigations revealed that the thickness of the ZIF-8 shell significantly influences the material’s performance. Among various configurations tested, the 2-ZnO@ZIF-8 sensor demonstrates the best formaldehyde detection properties, including high response (5 ppm, 5.03), excellent selectivity, short response and recovery times (29/40 s), excellent long-term stability, and a low theoretical detection limit (12.86 ppb) at 175 °C. The enhanced sensing properties can be attributed to the ZIF-8 surface’s high adsorption energy for formaldehyde molecules and the selective screening of gas molecules by ZIF-8. Overall, our study presents a promising strategy for developing highly selective gas sensors for formaldehyde detection, with the potential to contribute to improved indoor air quality monitoring and safety measures.

Uniform Li-ion diffusion and robust solid electrolyte interface construction for kilogram-scale Si@ZIF powder as the anode in Li-ion batteries

The zeolitic imidazolate framework (ZIF) is characterized by a highly ordered structure, large cavities, and thermal/chemical stabilities and has been widely researched for energy storage. In this study, using commercial Si powder with a diameter of 50–200 nm at a kilogram scale, Si@ZIF core-shell particles with dispersed ZIF-8 rhombic dodecahedrons were fabricated by a one-pot method and achieved excellent electrochemical performance. With the specific pore diameter and ordered network formed by membered rings, experimental results demonstrated that the ZIF-8 shell realized a uniform and accelerated Li+ diffusion route, alleviated volumetric expansion of the Si core, and constructed a LiF-concentrated robust solid electrolyte interface film with less unnecessary consumption of electrolyte and Li+. Density functional theory calculations verified the higher adsorption energy for Li-solvated clusters and the de-solvation effect on the surface of ZIF-8, which can increase Li+ concentration along the one-dimensional channels of 4-membered ring with a diameter similar to that of Li+ for high-speed and uniform Li+ intercalation. Furthermore, the large and elastic rhombic dodecahedrons formed by pure ZIF-8 buffered the volume change and maintained the integrity of the Si electrode during cycling. As a result, the Si@8Z anode achieved a reversible capacity of 818.5 mAh g−1 after 650 cycles at 1 A g−1 with a high initial coulombic efficiency of 88.2 % and outstanding rater performance even at 8 A g−1. Nevertheless, the capacity of the Si anode decreased to 0 mAh g−1 after 200 cycles. The present work clarifies the effect of ZIF on the performance of Si anodes and provides a simple method to modify commercial Si powder.

Simulation insights into the lipase adsorption on zeolitic imidazolate framework-8

Zeolitic imidazolate frameworks (ZIFs) have recently emerged as immobilization matrices for biomolecules, most notably enzymes. Understanding the key factors that dominate the enzyme's catalytic activity on/in ZIFs is crucial for the development of new immobilization matrices. In this work, a combination of the parallel tempering Monte Carlo simulation and all-atom molecular dynamics simulation is performed to study the orientation and conformation of the Candida rugose lipase (CRL) adsorbed on oppositely charged and neutral ZIF-8 (i.e., ZIF-8-COOH, ZIF-8-NH2, and ZIF-8-neutral) surfaces. The results show that CRL could adsorb on all ZIF-8 surfaces, with an ordered orientation obtained on charged ZIF-8 surfaces. ZIF-8-NH2 is a good candidate for CRL immobilization since it can maximize the catalytic activity of CRL. The native conformation of CRL is well preserved on all three surfaces due to the partially water-containing surface of ZIF-8. The results could provide theoretical support for the application of porous materials in enzyme immobilization.

A Voltammetric Biosensor Based on Glassy Carbon Electrode Modified with DsDNA/ZIF-8/CNT for Determination of Malathion

In this work, we constructed an electrochemical biosensor based on a glassy carbon electrode modified by dsDNA/ZIF-8/CNT for sensitive and selective measurement of malathion (MAL). First, we investigated the interaction between MAL and salmon sperm dsDNA by computational (molecular docking) and experimental (UV-visible spectroscopy, and electrochemistry) methods. Then, we prepared the ZIF-8/CNT sensor and immobilized dsDNA on it. The ZIF-8/CNT was characterized by fourier transform infrared spectroscopy, X-ray scattering spectroscopy, and field-emission scanning electron microscopy. We optimized the factors affecting the electrochemical response of MAL and immobilization of the dsDNA on the surface of ZIF-8/ CNT/GCE, such as microliter of ZIF-8/CNT, concentration of the dsDNA and the time required for immobilization of dsDNA on the surface of ZIF-8/CNT-GCE, the effect of buffer pH on the MAL accumulation, the effect of MAL accumulation time, and the effect of pH the measurement solution. After optimizing the effective parameters, we drew the calibration curve using the differential pulse voltammetry (DPV) technique and obtained the concentration range of 0.20-50.00 μM with a detection limit of 1.0 nM. Furthermore, the RSD% for five consecutive tests of 2.00 μM MAL was obtained 2.4%. Also, the dsDNA/ZIF-8/CNT sensor showed good recovery in fruit samples.

A theoretical chemistry framework to unravel the monolayer adsorption of geogenic anions on UiO-66 and ZIF-8 organometallic structures

The arsenic and fluoride adsorption equilibria of UiO-66 and ZIF-8 organometallic structures were analyzed and interpreted. Experimental isotherms were quantified at 20–40 °C and pH 7 for both geogenic pollutants. Density functional theory and statistical physics simulations were carried out to explain and characterize the interfacial interaction forces for the adsorption of these toxic geogenic anions. The adsorption properties of UiO-66 were superior to those of ZIF-8 for both geogenic anions. The maximum fluoride and arsenic adsorption capacities were 4.3 and 2.8 mmol/g, respectively. The best adsorption of fluoride and arsenic was obtained using UiO-66 at 20 °C and pH 7. These MOFs showed adsorption capacities up to double those reported for several adsorbents used in the depollution of water containing these geogenic pollutants. The adsorption of arsenic and fluoride on ZIF-8 structure was endothermic (16–31 kJ/mol), while the removal of both pollutants using UiO-66 MOF was exothermic (−26 – −41 kJ/mol). This adsorption behavior was associated with the presence of a multi-anionic mechanism for both arsenic and fluoride on ZIF-8 surface. On the other hand, a double monodentate interaction was found for the arsenic adsorption on the external UiO-66 surface due to steric restrictions for mass transfer, while the fluoride adsorption corresponded mainly to a mono-anionic interaction where the internal pore diffusion played a relevant role. The calculated energies for fluoride adsorption were higher than those obtained for arsenic removal indicating stronger interfacial interactions. These results demonstrate the promising potential of these MOF structures for developing cost-effective water treatment processes to remove arsenic and fluoride from groundwater.

N, S co-doped hollow carbon nanocages confined Fe, Co bimetallic sites for bifunctional oxygen electrocatalysis

Regulating pore architecture and electronic structure is of significance for improving oxygen electrocatalytic activity of M−N−C catalysts. Herein, N, S co-doped hollow carbon nanocages confined Fe, Co bimetallic sites (FeCo-NS-HNCs) are constructed through an efficient surface bridging strategy. The surface modifier of trithiocyanuric acid trisodium salt bridges Co doped ZIF-8 surface with Fe ions to promote the formation of Fe/Co-Nx sites. The synergistic coupling of metal sites and N, S co-doping manipulates the adsorption/desorption characteristics of M−Nx sites to optimize intrinsic activity. The Kirkendall effect constructs the hollow carbon nanocages, improving the accessibility of M−Nx sites. Benefiting from the ameliorated electronic structure and hollow porous architecture, FeCo-NS-HNCs displays excellent bifunctional oxygen electrocatalytic activity (ΔE = 0.655 V). The liquid and flexible Zn-air batteries of FeCo-NS-HNCs offer prominent power density and cycling stability. This work provides estimable insights into the structure design and activity regulation of M−N−C catalysts for Zn-air battery.

Synergistic coupling of NiFe-layered double hydroxide nanosheets with Co-doped porous interconnecting carbon frameworks for efficient bifunctional electrocatalysis

The design of low-cost and durable electrocatalysts with high catalytic performance of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the development of sustainable energy technologies. NiFe-layered double hydroxide (NiFe-LDH) is a promising electrocatalyst for OER, but the poor ORR activity limits its large-scale application as a bifunctional electrocatalyst in energy storage and conversion devices. The rational design of hierarchical nanohybrids is an effective strategy to construct bifunctional OER/ORR electrocatalysts. Herein, a high-performance OER/ORR bifunctional non-noble metal electrocatalyst (NiFe-LDH/CoNC-PIN) was projected. The Co-doped carbon frameworks with porous interconnecting networks (CoNC-PIN) is prepared by pyrolysis of ZIF-8/67 via a salt template strategy, followed by the uniform in situ growth of ultrathin NiFe-LDH nanosheets on CoNC-PIN to construct the hierarchical NiFe-LDH/CoNC-PIN hybrid. The molten NaCl template in pyrolysis activates the surface of ZIF-8/67 and connects them into porous carbon networks to improve the surface area, porosity and electronic conductivity of catalysts. Due to the efficient electron transfer and strong coupling between CoNC-PIN and NiFe-LDH, the NiFe-LDH/CoNC-PIN exhibits a small OER overpotential of 249 mV at 10 mA/cm2, a low Tafel slope of 27.7 mV/dec, an ORR half-wave potential of 0.80 V, and excellent durability and structural stability. This strategy provides a novel insight to fabricate advanced OER/ORR bifunctional non-noble metal electrocatalysts.