ZIF-67 Particles Research Articles

MoS2 Decorated on 1D MoS2@Co/NC@CF Hierarchical Fibrous Membranes for Enhanced Microwave Absorption.

The design and development of high-quality electromagnetic waves (EMW) absorbing materials play a vital role in combating the escalating negative effects of microwave radiation and interference. Herein, MoS2@Co/NC@CF fibrous membranes are successfully fabricated by electrospinning technology and carbonization, and a molybdenum disulfide (MoS2) layer is synthesized on the surface of these fibers via hydrothermal method. The seed-assisted growth method not only effectively avoids the accumulation and improves the loading of ZIF-67 particles, so as to ensure that the magnetic components in the fibers are evenly distributed in a wider range, rather than only intermittently present in some sites. Meanwhile, the introduction of semiconductor MoS2 as the shell further optimizes the impedance matching and improves the EMW absorption performance of the carbon fibrous membranes: the minimum reflection loss (RLmin) is -67.56dB, and the maximum effective absorption bandwidth (EABmax) is further expanded to 6.56GHz (2.1mm, 11.44-18GHz). This work provides a feasible method for developing high-efficient EMW-absorbing materials.

V2CTx MXene-derived porphyrin-based MOF modified with ZIF-67 as an ultra-stretchable and deformable double-network hydrogel for room temperature detection of dimethylamine

Stretchable and self-adhesive chemical sensors are highly appealing for wearable health and environmental monitoring applications. Here, for the first time, we report V2CTx MXene-derived Porphyrin-based MOF (V-PMOF) modified with Zeolite imidazole framework-67 (ZIF-67) for the room temperature detection of dimethylamine. V-PMOF is synthesized from V2CTx MXene using tetrakis(4-carboxyphenyl)porphyrin (TCPP) as a ligand via a solvothermal route. Thereafter, an optimized wt% ratio (1:1) of ZIF-67 and V-PMOF crosslinked by PVA/polypyrrole (Ppy) is put for lyophilization which yields the V-PMOF@ZIF-67 double-network (DN) hydrogel. Detailed morphological assessment reveals dodecahedron-shaped ZIF-67 particles are evenly distributed on the V-PMOF sheets which are encapsulated in the polymer matrix. This three-dimensional polymeric structure of hydrogel largely enhances the active sites on the surface with abundant oxygen vacancies. The sensor exhibits a dynamic range of 1 ppm to 13 ppm with a low limit of detection (LOD = 3s/σ) of 902 ppb towards dimethylamine detection. Further, quick response/recovery times (3 s/7 s) are observed along with high robustness tosignificant mechanical deformation, including twist (270°), large-range bending, and up to 500% strain without affecting the sensing performance. The remarkable sensitivity is accredited to the abundance of O2 functional groups in polymer chains and the formation of Schottky heterojunction between V-PMOF and ZIF-67, facilitating charge transfer between the heterostructure to dimethylamine during sensing. In addition, the self-adhesive hydrogel-based sensor shows outstanding selectivity against other typical volatile organic compounds (VOCs) such as acetone, ethanol, ammonia, trimethylamine, aniline, and methanol. In overall, this work provides insight into designing extremely flexible sensitive dimethylamine gas sensor as innovative material.

High-performance novel ZIF-67 and ZIF-67@MWNTs composite adsorbents for efficient removal of pharmaceutical contaminant from water: Exceptional capacity and excellent reusability

The removal of pharmaceutical waste products like ibuprofen (IBP) from water is very important for the environment and the health of human and aquatic organisms. In the present work, the adsorption of IBP from aqueous solution was investigated by synthesizing novel ZIF-67 and ZIF-67@MWNTs hybrid composite material by incorporating ZIF-67 particles with carboxyl functionalized multiwalled carbon nanotubes (COOH-MWNT). The synthesized ZIF-67 and ZIF-67@MWNTs adsorbents were characterized by the XPS, XRD, SEM, TEM, BET, FTIR, and TGA analysis to examine their physio-chemical properties. The synthesized novel ZIF-67 has a 1743 m2/g BET surface and 0.692 cm3/g total pore volume. The IBP adsorption process including isotherm and kinetic studies as well as the effect of different parameters i.e. pH, initial concentration, time, adsorbents, and their dosage were examined. Among all the synthesized composite materials, the ZIF-67@MWNT-50 mg material showed the highest IBP adsorption capacity of 841 ± 5 mg/g, about 467 ± 5 mg/g more than the ZIF-67 following the Langmuir and pseudo-second-order model. The enhancement in the IBP adsorption is because of the incorporation of COOH-MWNT and the presence of a large number of active binding sites which showed the van der Waal interactions, host–guest interactions, π- π interactions, and H-bonding between the adsorbate and adsorbent. For the detailed study of the IBP adsorption mechanism of ZIF-67, molecular dynamic (MD) simulations were performed. Additionally, the reusability of ZIF-67@MWNT-50 mg material via a simple regeneration method up to five cycles while maintaining about 96 % adsorption capacity of the pristine non-used ZIF-67@MWNT-50 mg material revealed its importance as an effective adsorbent for the adsorptive elimination of different pharmaceutical hazardous materials from water.

Shaping Phenolic Resin-Coated ZIF-67 to Millimeter-Scale Co/N Carbon Beads for Efficient Peroxymonosulfate Activation.

Catalytic performance decline is a general issue when shaping fine powder into macroscale catalysts (e.g., beads, fiber, pellets). To address this challenge, a phenolic resin-assisted strategy was proposed to prepare porous Co/N carbon beads (ZACBs) at millimeter scale via the phase inversion method followed by confined pyrolysis. Specially, p-aminophenol-formaldehyde (AF) resin-coated zeolitic imidazolate framework (ZIF-67) nanoparticles were introduced to polyacrylonitrile (PAN) solution before pyrolysis. The thermosetting of the coated AF improved the interface compatibility between the ZIF-67 and PAN matrix, inhibiting the shrinkage of ZIF-67 particles, thus significantly improving the void structure of ZIF-67 and the dispersion of active species. The obtained ZACBs exhibited a 99.9% removal rate of tetracycline (TC) within 120 min, with a rate constant of 0.069 min-1 (2.3 times of ZIF-67/PAN carbon beads). The quenching experiments and electron paramagnetic resonance (EPR) tests showed that radicals dominated the reaction. This work provides new insight into the fabrication of high-performance MOF catalysts with outstanding recycling properties, which may promote the use of MOF powder in more practical applications.

N-doped porous carbon with ZIF-67-derived CoFe2O4-Fe particles for supercapacitors

The development of novel materials for electrodes with high energy densities is essential to the advancement of energy storage technologies. In this study, N-doped layered porous carbon with ZIF-67-derived binary CoFe2O4-Fe particles was successfully fabricated by the pyrolysis of an Fe-based chitosan (CS) hydrogel mixed with ZIF-67 particles. Various characterization techniques were employed to assess the performance of the prepared porous CoFe2O4-Fe@NC composite. This composite exhibits excellent performance owing to the effective combination of multivalent CoFe2O4-Fe particles derived from ZIF-67 with N-doped porous carbon substances with a high surface area, which helps to accelerate ion and charge transfer. The specific capacitance of the CoFe2O4-Fe@NC composite carbonized at 700 °C reached 3960.9F/g at 1 A/g. When this composite is combined with activated carbon (AC) to construct an asymmetric supercapacitor (ASC), a density of energy of up to 84.9 W h kg−1 is attained at a power capacity of 291.6 W kg−1. Moreover, this composite maintained a capacitance retention of up to 94.9 % after 10,000 cycles. This work offers new perspectives on high-performance supercapacitors and their applications.

Designing MOFs/CuCo-LDHs hybrid-based superhydrophobic sponge for speedy eliminating microplastics, dyes, and oils from high-salinity water

It is urgent to develop effective materials to decontaminate wastewater owing to water scarcity in the whole world. In this study, we successfully fabricated a superhydrophobic and superoleophilic MOFs/LDHs based-functional sponge (OMCTS/ZIF-67/CuCo-LDHs@Sponge) with large specific surface area and high porosity for the first time through a two-step co-precipitation method and surface modification of polysiloxane. The polydopamine (PDA) molecules not only greatly improved the adhesion between coatings and substrate, but also enhanced growth of MOFs and LDHs structure. The in-situ growth of hexahedron ZIF-67 particles on multiple layered CuCo-LDHs sphere formed heterojunction, which significantly increased adsorption sites, specific area, and porosity and also solved the aggregation problem of powder MOFs. The CuCo-LDHs with large surface area was beneficial to ZIF-67 growth owing to same Co2+connection. The developed superhydrophobic sponge not only quickly and selectively absorbed various microplastics (MPs, as high as 500 mg/mL), dyes (C0 = 40 mg/L, removal rate of 99.6 %), and emulsified oils from high-salinity water with high capacity (e.g. 85 mg/g for PP-2000, 94 mg/g for PS-100, and 93 mg/g for PE-2000), but also exhibited outstanding synchronous decontamination capability for coexisting pollutants through multi-molecular synergistic mechanism and multiple adsorption forces (grasping force, strong capillarity, electrostatic interaction, hydrogen bonds, π-π interactions, p-π conjugation interaction. Van der Waals forces). The coated sponge showed superior mechanical durability, which still maintained separation ability above 98 % after repeated adsorption of MPs for 40 cycles. The adsorption mechanism was detailly investigated through theoretical simulation of adsorption energy. This coated sponge was destined to show broad and useful applications in water purification field.

Hollow Ti3C2Tx MXene sphere-based ZIF-67 derived central radiative cobalt-tipped carbon nanotubes electrocatalysts for ORR and OER

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a key role in many renewable energy conversion and storage technologies. As the state-of-the-art ORR and OER electrocatalysts, noble-metal-based electrocatalysts suffer from high price, low earth abundance, single functionality, and poor stability. Developing high performance noble-metal-free ORR and OER bifunctional electrocatalysts as alternatives is highly desirable but remains a significant challenge. In this work, we reported a metal-organic-framework-engaged strategy for the fabrication of central radiative cobalt-tipped N-doped carbon nanotube/hollow Ti3C2Tx sphere composites (h-Ti3C2Tx@Co-NCNT), in which ZIF-67 particles were in situ grown on spherical structure composed of Ti3C2Tx nanosheets constructed with hard template PMMA and then were converted to cobalt-tipped N-doped carbon nanotubes through a pyrolysis process. The hollow Ti3C2Tx nanosheets sphere not only served as conductive scaffolds for the growth of Co-NCNT but also balanced the tradeoff between graphitization of carbon and the surface area. Benefiting from the abundant Co-N/C active sites, reasonably high graphitization of carbon and suitable surface areas, the optimized h-Ti3C2Tx@Co-NCNT manifested comparable ORR (half-wave potential of 0.843 V) and OER (overpotential of 323 mV) activities. In addition, the h-Ti3C2Tx@Co-NCNT assembled zinc-air battery exhibits superior performance beyond commercial Pt/C+RuO2. Certificating this strategy can provide great opportunity for its application in renewable conversion and storage technologies.

Synergistic photoinduced charge transfer resonance from porous ZIF-67 decorated violet phosphorus array for SERS immunoassay of SARS-CoV-2 spike protein

As a rapid, highly sensitive, and user-friendly technique, surface-enhanced Raman scattering (SERS) has an extraordinary appeal to home self-test of COVID-19 during the post pandemic era. However, most of the existing SERS substrates have been still criticized in stability, repeatability, and sample enrichment. To address these obstacles, a novel non-metallic SERS substrate with porous surfaces and array geometry was developed by in-situ growing ZIF-67 particles on two-dimensional violet phosphorus (VP) matrix. Chemical enhancement was prominently promoted by the synergistic photoinduced charge transfer resonance in the hybrid band structure of the ZIF-67@VP substrate, facilitating a noble metal-similar enhancement factor of 6.11 × 107. The biocompatible ZIF-67@VP porous array with attractive enhancement capability and high anchoring efficiency was further utilized to monitoring SARS-CoV-2 spike protein in practical saliva samples based on a sandwich immunostructure, achieving a limit of detection of 1.7 ng/mL assisted by black phosphorus nanosheets. This nonmetallic immunoassay strategy with exceptional sensitivity and specificity is predicted to extend the utilization of SERS obstacle in daily infectious disease screening.

Anisotropic Interface Successive Assembly for Bowl-Shaped Metal-Organic Framework Nanoreactors with Precisely Controllable Meso-/Microporous Nanodomains.

Colloidal metal-organic framework (MOF) nanoparticles, with tailored asymmetric nanoarchitectures and hierarchical meso-/microporosities, have significant implications in high-performance nanocatalysts, nanoencapsulation carriers, and intricate assembly architectures. However, the methodology that could achieve precise control over the anisotropic growth of asymmetric MOF particles with tailored distributions of meso- and microporous regions has not yet been established. In this study, we introduce a facile anisotropic interface successive assembly approach to synthesize asymmetric core-shell MOF (ZIF-67) nanobowls with worm-like mesopores in the core and intrinsic micropores in the shell. Our synthesis pathway relies on anisotropic nucleation of mesoporous MOF nanohemispheres on emulsion interfaces through the cooperative assembly of surfactants and MOF precursors. This is followed by the growth of microporous MOF layers on both interfaces of mesoporous cores and emulsion droplets, resulting in a hierarchically porous core-shell nanostructure. By utilizing this multi-interface-driven approach, we enable the creation of diverse geometries and distributions of mesopores and micropores in asymmetric MOF nanoarchitectures. The obtained bowl-like meso-/microporous core-shell ZIF-67 particles exhibit enhanced catalytic activity for CO2 cycloaddition, attributed to reactant accumulation within the bowl-like architecture, active site accessibility in the open mesoporous core, and improved structural stability. Overall, our study provides insights and inspiration for exploring the intricate asymmetric nanostructures of hierarchically porous MOFs with diverse potential applications.

Zeolitic imidazolate framework-67 enabled cellulosic paper for efficient particulate matter capture

The combination of functional zeolitic imidazolate frameworks (ZIFs) with suitable substrates is promising for the preparation of advanced filtering materials. In this study, the bleached kraft softwood pulp (NBKP) was composited with ZIF-67 particles via an in situ growth method to fabricate functional paper. Enabled by the traditional papermaking process, ZIF-67 crystals were uniformly and tightly anchored on cellulosic fibers in a facile and economic way. The introduction of ZIF-67 boosted the mechanical performances of the composite paper owing to the presence of electrostatic interactions and hydrogen bonds. Meanwhile, the resultant paper presents hierarchical porous structure with a large specific surface area of 327.07 m2·g−1. The filters with hierarchical pore structure will provide a complex tortuous channel for passing particulates, which can increase the frequency of effective collision between filters and particulates. Air filtering tests demonstrated that the ZIF-67 entrapped paper has superior particle removal efficiency with a low pressure drop and a large dust holding capacity. The optimal ZP-3 sample displayed removal efficiencies of 98.52 % for PM2.5 and 99.00 % for PM10. Meanwhile, filtration quality factors were calculated to be 0.15 (PM2.5) and 0.17 (PM10), respectively. The filter also has good antibacterial activity. In addition, ZP-x composite paper is easy to regenerate and possesses good reusability. The high-efficient ZP-x filter will have potential applications in fields of air purification.

ZIF-67 derived material encapsulated V2O3 hollow sphere structure of Co-NC@V2O3-sp used as a positive electrode material for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries receive considerable attention for their high energy density, but their slow reaction kinetics and poor shuttle effects raise concerns. Here, synthesized V2O3 spheres were used as substrate templates, and ZIF-67 particles were grown on the surface of V2O3 by in-situ growth method. ZIF-67 was calcined at high temperature to form N-doped porous carbon attached to the surface of V2O3 spheres (Co-NC@V2O3-sp). The hollow structure of V2O3 spheres provided abundant buffer space for sulfur volume expansion and enhanced the stability of the battery cycle. In addition, the great pore volume and specific surface area resulted in abundant active physical and chemical sites, the strong chemical adsorption of V4+ effectively trapped polysulfides, and the cobalt nanoparticles on the surface effectively consolidated the active sites. The rapid transformation between shuttle effect and polysulfides were limited by physical coordination and chemisorption, respectively. Owing to this double synergistic effect, the prepared composites had an initial discharge capacity of 1483 mAh g−1 (0.1 C). The initial specific capacity reached 1002 mAh g−1 (0.5 C), and it achieved 645 mAh g−1 after 500 cycles. These results showed that Co-NC@V2O3-sp has high electrochemical function in Li-S batteries.

A sensitive ZIF-67/ MWCNTs composite-based sensor for the detection of sunset yellow in food and beverages

This study introduces an innovative sensing platform designed for the detection of sunset yellow (SY). The platform employs a composite electrode material comprising of a zeolitic imidazole framework (ZIF-67) and multiwalled carbon nanotubes (MWCNTs) on a glassy carbon electrode (GCE). The synergy between ZIF-67 and MWCNTs leads to an enhancement in the electrochemical sensing behaviour for SY oxidation. Notably, the electrostatic interaction between ZIF-67 particles and MWCNTs results in a 6.26-fold increase in the current response. Additionally, the charge transfer resistance (Rct) was remarkably low, measuring at only 114 Ω. Under ideal conditions, the SY sensor demonstrated a minimum detectable concentration (LOD) and quantifiable concentration (LOQ) of 0.103 and 0.343 µM, respectively. The detection of SY was effectively conducted in snacks and beverages, showcasing its practical applicability. The results obtained demonstrate exceptional mean relative standard deviations (RSDs) < 1 %, indicating high precision. Additionally, the recovery ranges achieved, ranging from 95 % to 105 %, validate the sensor’s reliability and accuracy. Furthermore, the chemical reactivity of SY was investigated through density functional theory (DFT) calculations, which identifies the redox-reactive site in SY, aligning with the postulated reaction mechanism observed in cyclic voltammograms. Monte Carlo (MC) simulations provide insight into the electrostatic and covalent interactions between the functional groups of the analyte and the designed sensor. This novel sensing approach demonstrates significant promise in the identification and surveillance of artificial food colourants in the food manufacturing sector.

Assessment of synthesis conditions on the corrosion inhibitive features of ZIF-67 MOF

Metal-organic frameworks (MOFs) have indeed attracted substantial interest owing to their distinctive features and diverse applications, such as corrosion protection. In this work, using two synthesis methods, namely co-precipitation (CZ67) and solvothermal (SZ67), a cobalt-based zeolitic imidazole framework (ZIF-67) was developed as an essential family of MOFs. The results of the characterization confirmed that ZIF-67 particles were synthesized successfully. According to the results of XRD, FE-SEM, TEM, ICP-OES, TGA, and BET analysis, the SZ67 has a higher surface area and higher stability in solution compared to CZ67. In addition, CZ67 and SZ67 were introduced in epoxy coatings to form CZ67/EPC and SZ67/EPC. The SZ67/EPC exhibited greater corrosion inhibition activity than the CZ67/EPC. After 24 h of exposure to the salty media, the|Z|at the low frequency for the scratched SZ67/EPC (119,500 Ω.cm2) reached 1.1 and 5.7 times of that for the CZ67/EPC and Neat epoxy coatings, respectively. Furthermore, SZ67/EPC demonstrated superior barrier anticorrosion properties during immersion for forty days. The corrosion protection and adhesion performance of SZ67/EPC surpassed the rest of the coated samples after salt spray exposure.

2-Methylimidazole-induced synthesis of ZIF-67/CuO composite catalysts for enhanced oxygen evolution reaction activity

Developing high-efficient Cu-based catalysts for oxygen evolution reaction (OER) remains challenging under alkaline conditions. Herein, a series of ZIF-67/CuO composite catalysts on Cu foam (CF) were synthesized under controlling the molar ratio of Co2+ to 2-Methylimidazole. The formation of CuO nanobelts (NBTs) from CF and subsequent epitaxial growth of ZIF-67 particles facilitate the synergistic effect between components, which could enhance the charge/mass transfer in the electrocatalytic water oxidation process to achieve excellent OER activity. The optimal ZIF-67(R48)/CuO/CF composite sample obtained current densities of 50 and 200 mA cm–2 in 1.0 mol L–1 KOH with an overpotential of only 295 and 344 mV. Especially, the composite catalyst showed good stability on running 50 h at 20 mA cm–2 without obvious decay. The Cu-ZIF layer at the interface of ZIF-67 and CuO enabled fast electronic transfer between Cu and Co sites during the OER process, which is the key issue for excellent OER activity of the composite catalysts.

ZIF-67 Incorporated Sulfonated Poly (Aryl Ether Sulfone) Mixed Matrix Membranes for Pervaporation Separation of Methanol/Methyl Tert-Butyl Ether Mixture.

Mixed matrix membranes (MMMs) with nano-fillers dispersed in polymer matrix have been proposed as alternative pervaporation membrane materials. They possess both promising selectivity benefiting from the fillers and economical processing capabilities of polymers. ZIF-67 was synthesized and incorporated into the sulfonated poly (aryl ether sulfone) (SPES) matrix to prepare SPES/ZIF-67 mixed matrix membranes with different ZIF-67 mass fractions. The as-prepared membranes were used for pervaporation separation of methanol/methyl tert-butyl ether mixtures. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and laser particle size analysis results show that ZIF-67 is successfully synthesized, and the particle size is mainly between 280 nm and 400 nm. The membranes were characterized by SEM, atomic force microscope (AFM), water contact angle, thermogravimetric analysis (TGA), mechanical property testing and positron annihilation technique (PAT), sorption and swelling experiments, and the pervaporation performance was also investigated. The results reveal that ZIF-67 particles disperse uniformly in the SPES matrix. The roughness and hydrophilicity are enhanced by ZIF-67 exposed on the membrane surface. The mixed matrix membrane has good thermal stability and mechanical properties, which can meet the requirements of pervaporation operation. The introduction of ZIF-67 effectively regulates the free volume parameters of the mixed matrix membrane. With increasing ZIF-67 mass fraction, the cavity radius and free volume fraction increase gradually. When the operating temperature is 40 °C, the flow rate is 50 L·h-1 and the mass fraction of methanol in feed is 15%, the mixed matrix membrane with ZIF-67 mass fraction of 20% shows the best comprehensive pervaporation performance. The total flux and separation factor reach 0.297 kg·m-2·h-1 and 2123, respectively.

Ag@ZIF-67 nanocomposites for ultra-sensitive SERS detection to thiram molecules

Surface-enhanced Raman scattering technique has become a powerful tool for detecting trace targets in the field of food-safety. However, it is a challenge to regulate the hot spots of the detection substrate and its interaction with target molecules for the enhancement of SERS activity. Herein, we reported the high performance SERS substrate based on Ag@ZIF-67 nanocomposite with sugar-coated haws like structure. It was found that the coverage of ZIF-67 particles on the surface of Ag nanowires can adjust the SERS ability of detection substrate. Compared with pure Ag nanowires, functionalized Ag nanowires exhibit outstanding SERS activity with good stability and uniformity. The detection limit of crystal violet and thiram can be as low as 10−10 M and 10−8 M, respectively. After 35 d, the SERS activity remains basically unchanged. Furthermore, it also has excellent SERS response to 5 10−5 M thiram residues on the surface of vegetables. Such high SERS activity can be attributed to the enrichment and screening molecular effect of porous ZIF-67 nanoparticles, and the surface plasmon resonance effect of Ag nanowires. This work provides a simple strategy for the on-site detection of pesticide residues in the actual applications.

A monolithic gold nanoparticle@metal-organic framework composite as CO2 photoreduction catalyst

The application of metal-organic frameworks (MOFs), especially MOF composites, has been hindered by a lack of method to process powders into useable forms. To address this challenge, we report here a low temperature synthesis method that enables direct formation of a densified monolithic MOF composite, i.e. Au@ZIF-67. The monolithic composite contains Au nanoparticles (Au NPs) that are well-dispersed and encapsulated within ZIF-67 particles. It exhibits high surface area, bulk density, and mechanical robustness as observed in monolithic ZIF-67, while retaining the localized surface plasmonic resonance (LSPR) characteristic of Au NPs. Benefiting from this unique combination, the monolithic Au@ZIF-67 samples display an enhanced CO2 photoreduction performance under visible light—with the best-performing Au@ZIF-67 sample showing a volumetric CO production rate 1.5 and 3 times higher compared to the pristine monolithic ZIF-67 and ZIF-67 powder, respectively.

Comparative study of Mn-ZIF-67 derived carbon (Mn-Co/C) and its rGO-based composites for the methanol oxidation

In this study, we report the comparative electrocatalytic study of commercial Pt/C with Mn-Co/C and its rGO based composites (i.e., 1–8 wt% rGO @Mn-Co/C) for methanol oxidation. Catalysts were synthesized by a two-step procedure. Firstly, via the solvothermal method, all catalysts were prepared and then pyrolyzed at 700 °C in an argon and hydrogen mixture environment. The characterization of the Mn-Co/C, 1–8 wt% rGO Mn-Co/C catalysts was accomplished by XRD, SEM, EDX, Raman, TEM, BET and XPS. The as-prepared dodecahedron morphology of the initial Mn-based ZIF-67 particles is retained, with the interconnected sheets of reduced graphene oxide after the pyrolysis in a reducing atmosphere (i.e., Ar+H2). Among all the catalysts, the 5 wt% rGO@Mn-Co/C catalyst has shown much higher electrochemical activity (i.e., 235.24 mA/cm2) and stability than other rGO-based Mn-Co/C catalysts and also than commercial Pt/C in 1 M NaOH and 3 M CH3OH. The presence of support materials such as rGO and the availability of nano porous carbon with Mn and Co may contribute to the improved electrocatalytic activity of 5 wt% rGO Mn-Co/C over Mn-Co/C. With a number of beneficial features in structure, composition, and nitrogen doping level, it results in enhanced electrocatalytic activity and stability as well as methanol tolerance when benchmarked with a commercial Pt/C electrocatalyst under the same testing conditions.

Multilayered Mesoporous Composite Nanostructures for Highly Sensitive Label-Free Quantification of Cardiac Troponin-I.

Cardiac troponin-I (cTnI) is a well-known biomarker for the diagnosis and control of acute myocardial infarction in clinical practice. To improve the accuracy and reliability of cTnI electrochemical immunosensors, we propose a multilayer nanostructure consisting of Fe3O4-COOH labeled anti-cTnI monoclonal antibody (Fe3O4-COOH-Ab1) and anti-cTnI polyclonal antibody (Ab2) conjugated on Au-Ag nanoparticles (NPs) decorated on a metal–organic framework (Au-Ag@ZIF-67-Ab2). In this design, Fe3O4-COOH was used for separation of cTnI in specimens and signal amplification, hierarchical porous ZIF-67 extremely enhanced the specific surface area, and Au-Ag NPs synergically promoted the conductivity and sensitivity. They were additionally employed as an immobilization platform to enhance antibody loading. Electron microscopy images indicated that Ag-Au NPs with an average diameter of 1.9 ± 0.5 nm were uniformly decorated on plate-like ZIF-67 particles (with average size of 690 nm) without any agglomeration. Several electrochemical assays were implemented to precisely evaluate the immunosensor performance. The square wave voltammetry technique exhibited the best performance with a sensitivity of 0.98 mA mL cm−2 ng−1 and a detection limit of 0.047 pg mL−1 in the linear range of 0.04 to 8 ng mL−1.

Flower-like three-dimensional bifunctional cathode catalyst for high-performance Li–O2 batteries: ZIF-67@3D-N/rGO

To accelerate the practical application of Li–O2 batteries. A catalyst with outstanding oxygen reduction reaction and oxygen evolution reaction catalytic activity is required. Here, in-situ growth ZIF-67 within three-dimensional nitrogen-doped reduced graphene oxide (3D-N/rGO) layers was used to investigate a bifunctional catalyst. The inner space is supported by ZIF-67 particles, while 3D-N/rGO extends a suitable three-phase reaction interface and enhances O2 adsorbability. When assembled battery with normal electrolyte, it delivered a high specific capacity of 12028 mAh g−1, and stabilised for 203 cycles at 200 mA g−1 with a limited capacity of 500 mAh g−1. When LiBr-gel polymer electrolyte (GPE) was used instead of electrolyte the lithium metal anode, the polarisation value of LiBr-GPE in Li/Li batteries was only about 0.0384 V after continuous working for 1600 h. When used as a cathode catalyst in Li–O2 batteries, the electrode performance was doubled compared with using the normal electrolyte. These findings pave the way for developing of all-encompassing battery materials with high capacity and long cycle life.