Recently, the food freshness indicator (FFI) has garnered great interest from consumers and food producers. A novel FFI based on bacterial nanocellulose (BNC)/zeolitic imidazolate framework-L (ZIF-L) ...and grape anthocyanins was developed and characterized using field emission scanning electron microscopy, Fourier-transform infrared, X-ray diffraction, water contact angle, and BET techniques. The results confirmed that the BNC fibrils were decorated by in situ growth of ZIF-L, with a 3D flower-shaped structure and randomly multiple sharp-edged petals, and hydroxyl and oxygenated heterocycle aromatic ring functional groups on its surface. The reversibility, color stability performance, and moisture sorption of FFI were studied and its applicability in a two-layer arrangement as a visual freshness monitoring of shrimp and minced beef was evaluated. The FFI was able to distinguish (ΔE > 5) the fresh, medium fresh, and spoiled minced meat and shrimp visually during 10 and 4 days of storage at 4 °C, respectively. Also, monitoring of food chemical and microbiological parameters approved the correlation of food spoilage with the color parameters of FFI. These results confirmed the function of ZIF-L in the fabrication of highly pH-sensitive food intelligent packaging material.
•Zeolitic imidazolate framework-L (ZIF-L) was synthesized.•ZIF-L was used for the development of freshness indicator.•ZIF-L and grape anthocyanins were successfully embedded in the bacterial nanocellulose membrane.•The freshness indicator distinctly differentiated shrimp and minced beef freshness/spoilage steps.
Template‐free self‐assembly synthesis of nano‐sized metal‐organic frameworks (MOFs) is of particular interest in MOF research since organized nanostructures possessing distinctive properties are ...useful for many advanced applications. In this work, the facile room temperature synthesis of robust submicrometer‐sized ZIF‐71 crystals with different particle sizes (140, 290, or 430 nm), having a high permanent microporosity (SBET = 827 cm2 g−1) and synthesis yield up to 80% based on Zn on a gram‐scale, is reported. These small ZIF‐71 particles are ideal filler for the fabrication of thinner and homogeneous polydimethylsiloxane (PDMS) based mixed matrix membranes (MMMs) with excellent filler dispersion and filler‐polymer adhesion at high loading up to 40 wt%, as confirmed by scanning electron microscopy. Pervaporation tests using these submicrometer‐sized ZIF‐71 filled MMMs show significant improvement for bioethanol recovery. Interesting phenomena of i) reversible ethanol‐ethanol hydrogen interaction in the ethanol liquid‐phase and ii) irreversible hydrogen interaction of ethanol and –Cl functional group in the α‐cages and octagonal prismatic cages of ZIF‐71 in ethanol vapor‐phase are discovered for the first time by a Fourier transform infrared spectroscopy (FTIR) study. In full agreement with molecular simulation results, these explain fundamentally the ZIF‐71 filled MMMs pervaporation performance.
Gram scale synthesis of submicrometer‐sized ZIF‐71 crystal is demonstrated via a simple mixed solvent approach for improving mixed matrix membrane pervaporation separation of bioethanol. The host–guest chemistry at its molecular level is unravelled by grand canonical Monte Carlo simulation and FTIR spectroscopy. The results reveal a strong hydrogen interaction between the cages of ZIF‐71 and ethanol, well explaining the pervaporation performance.
Summary
ZIF‐7‐III and its nitrogen‐doped porous carbon (NPC) structures were synthesized for the first time by direct carbonization and fused with KOH in an argon atmosphere. The morphology and ...structural characterization of NPC materials were performed by scanning electron microscopy (SEM), Raman, Fourier transform infrared (FT‐IR), and X‐ray diffraction (XRD) analysis, and their supercapacitive properties were examined as a device form for the first time. The characteristic peak at 2θ = 9.1° in the XRD pattern indicates pure ZIF‐7‐III phase obtained, and impurity was not observed in the phase of ZIF‐7‐III. Two broad peaks at nearly 25° and 44° might belong to graphite and its diffractions for the NPC structures. The FT‐IR analysis of ZIF‐7‐III and NPC materials matches well with the reported literature. Raman spectra of the activated NPC material show two prominent peaks located around 1357 and 1592 cm−1. A nonporous dense phase with a 2D stacked‐layered structure was detected on the structure of ZIF‐7‐III. The morphology of activated NPC material turns into the 2D structure to the 3D dodecahedron morphology with an increase in the specific surface area. The cyclic voltammetry and galvanostatic cycling measurements of NPC structures were investigated on the device system in different electrolytes such as KOH, NaOH, LiOH, and Na2SO4. The electrochemical performance of NPC compounds was presented comparatively in a device, and the KOH‐activated NPC material showed a higher specific surface area (709.7 m2/g) and higher capacitance value (104 Fg−1 at 0.4 Ag−1 and 118 Fg−1 for 5 mV/s) with low capacitive fade after 4000 charge/discharge cycles among others.
Nitrogen‐doped porous carbon and their activated derivatives were produced and electrochemical performances were presented comparatively in a device form with different electrolytes systems.
Controlled ratio mixed Co and Zn 2-methylimidazolate could be synthesized in one pot mixing.
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•A series of Co and Zn mixed ZIF were prepared by one pot mixing.•Proportional inclusion ...of the two metals in the products was confirmed.•The mixed metal ZIFs are found to form larger particles compared to the single metal analogs.•Adsorption of As(V) was tested.•Co-rich materials are more efficient at adsorbing As(V) from alkaline pH.
One-pot synthesis of ZIF-8, ZIF-67, and a series of their mixtures was carried out in ambient conditions. Among the two reagents used for the deprotonation of 2-methylimidazole (2-mim), only ZIF-67 could be formed in the presence of both sodium hydroxide and trimethylamine. In contrary, no trace of ZIF-8 was observed when trimethylamine was used. About the solvents, because ZIF-67 could not be prepared in aqueous condition, for the given metal to ligand ratio, methanol was used for all. Once the most favorable condition was set, ZIF-8 (Zn(2-mim)2) and ZIF-67 (Co(2-mim)2), and the mixtures Zn0.9-0.1Co0.1-0.9(2-mim)2 were successfully synthesized. The composition of the mixture ZIFs was found to be nearly in proportion with the mixing ratios of the Zn and Co salts. The XRD patterns of ZIF-8, ZIF-67, and the mixtures were found to be finely matching. However, the crystallite sizes of the mixtures were relatively larger than both the pure materials. FT-IR shows up to 2% red-shift of some major peaks with the change from ZIF-8 to ZIF-67. TG-DTA showed a sharp drop in the decomposition temperature with the introduction of Co into the framework. About the arsenate ion adsorption, all the materials could uptake AsO4 anion from KH2AsO4 solution, basically following the same mechanism, ligand exchange. Yet, for the basic pH solution, ZIF-67 and the Co-rich mixtures show surprisingly higher adsorption capacity.
Simultaneously achieving both bifunctional catalysts and flexible self-supported electrodes are urgently in demand to satisfy rechargeable lithium-oxygen (Li-O2) batteries, particularly for wearable ...devices. Herein, we propose a novel strategy embracing electrospinning and hot-pressing to develop Co-based composites embedded in porous nitrogen-rich carbon nanofibers (ZnCo-NC/NCF) as a freestanding cathode for Li-O2 batteries. The fabricated electrode is obtained through pyrolysis of bimetallic (ZnCo) zeolitic imidazolate frameworks/polyacrylonitrile (PAN) nanofibers (BMZIF/PAN). Benefiting from outstanding mechanical strength of electrospun carbon matrix and abundant porosity originated from decomposition of ZIFs as well as fully exposed Co-Nx active sites, the achieved cathode is capable of excellent flexibility, high specific surface area, great conductivity and good catalytic behaviors towards both oxygen reduction/evolution reactions. Consequently, the corresponding Li-O2 batteries exhibit remarkably decreased voltage gap (0.49 V), high specific areal capacity (9.52 mAh cm−2) and long-term cycling capability (around 42 cycles under a curtailing capacity of 0.25 at 0.04 mA cm−2). Besides, the evolution of the morphology and electrochemical impedance spectroscopy at various reaction states are further investigated, which confirms that ZnCo-NC /NCF cathode enables formation and decomposition of lithium peroxide during charge-discharge period.
The development of efficient catalysts is essential to promote slow hydrogen reaction kinetics in alkaline solutions. Herein, an ultrathin ZIF-derived efficient HOR/HER electrocatalyst, with Co ...single-atom-anchored RuCo clusters on N-doped graphitized carbon nanosheets (RuCo/SANC NS), is designed and constructed by a step-by-step calcination strategy. In the RuCo/SANC NS, Co atoms dispersed in carbon nanosheets induce the formation of ultrasmall RuCo clusters and stabilize the RuCo clusters. Abundant coordinatively unsaturated Ru sites are formed on the surface of RuCo clusters due to the small size effect. The electronic structure of the Ru site is regulated by the alloying effect with Co, optimizing the adsorption energy to *H and *OH and accelerating the HER/HOR kinetics. The RuCo/SANC NS catalyst exhibits excellent mass activity with HER of 13.58 A/mgRu and HOR of 3.85 A/mgRu, which are about 35.35 and 48.13 times that of Pt/C.
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•RuCo clusters are stabilized by Co single atoms dispersed on ultrathin carbon sheets.•The small size effect induces abundant coordinatively unsaturated Ru atoms.•The electronic structure of Ru sites is regulated by the alloying effect with Co.•Ru–Co synergy reduces the reaction energy barrier of the Volmer step.•Increased d-orbital electron density at Ru enhances resistance to CO toxification.
In recent years, bifunctional electrocatalysts derived from zeolite imidazole framework (ZIF) as a carbon substrate have been a hot research topic. In addition, one-component catalyst cannot achieve ...the efficient catalysis of oxygen reduction reaction(ORR) and oxygen evolution reaction( OER). At the same time, this paper reports a bifunctional catalyst with a bimetallic three-dimensional porous structure using silicon spheres as a hard template and ZIF as a carbon substrate. The inherent porosity of pie-shaped ZIF, the use of silica templates to generate an ordered macroporous structure, and the synergy between metal activity sites, which together promote the mass transfer and electrocatalytic activity of the battery. The synthesized catalyst showed excellent electrocatalytic activity toward ORR and OER including a half-wave potential (E1/2 =0.80 V) which is 20 mv less than Pt/C, and its overpotential (0.321 V) and voltage gap (ΔE=0.751 V) surpasses commercial Pt/C+RuO2 catalyst (0.368 V, ΔE=0.778 V). Moreover, primary and rechargeable Zn-air battery is assembled based on this catalyst delivered preferable performance, including a high power density (98.7 mw cm-2),batter charge/discharge cycling stability (220 h) exceeds commercial Pt/C+RuO2 catalyst (160 h）. Given its unique pore structure and good electrical conductivity, this derived material has scope for expansion in bifunctional catalysis and other energy technologies for rechargeable Zn-air batteries.
•Synthesis of bifunctional electrocatalysts by secondary metal doping strategy.•One-step pyrolysis to obtain an ordered porous structure.•Voltage gap superior to that of precious metal catalysts.•Fe@Co-NMC-900 has better cell cycle stability than noble metal catalysts.
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•ZAC@VS2 disperses the modified tubular carbon material in VS2 lamella.•ZAC@VS2 has improved active sites and conductivity.•ZAC@VS2 shows considerable specific capacitance and low ...charging resistance.•ZAC@VS2 electrode displays a prominent heavy metal ions of lead (II) adsorption capacity and rate.•ZAC@VS2 electrode has the superior ion selectivity to Pb2+ than Fe3+ and Na±.
The conventional separation technologies, like chemical precipitation and adsorption processes, cannot quickly and selectively separate and recycle heavy metal ions from waste. Due to its rich sulfur content and excellent electrical conductivity, vanadium disulfide is a potential material for effectively removing lead from wastewater. The vanadium disulfide material with selective adsorption ability was introduced into CDI technology to construct a coupling technology with both advantages. The N-doped modified ZIF@vanadium disulfide (ZAC@VS2) composites were successfully synthesized by hydrothermal method. Electrosorption experiments show that ZAC@VS2 material presents the remarkable saturated adsorption capacity to lead(II) ions (239.52 mg/g) in the 500 mg/L PbCl2 solution. In the triplex blend system (Fe3+/Pb2+/Na+) with each solute density of 100 mg/L, the saturated adsorption efficiency of 85.4% to Pb2+ can still be maintained. In addition, compared with the Langmuir(R2=0.873) adsorption isotherm model, the Freundlich model (R2=0.922) can be better used to fit the adsorption process, which proves that the adsorption process is multilayered and heterogeneous. XPS tests and competitive adsorption experiments show that the electric double layer (EDL) and complexation together promote the selective adsorption of heavy metal ions by ZAC@VS2. ZAC@VS2 composite electrode shows excellent performance in the removal of lead ions in battery waste liquid, indicating the potential of introducing ZAC@VS2 into CDI to remove lead ions.
One-step hydrogenation of phenol is a preferable and economic route for preparing cyclohexanone. The development of catalysts with high catalytic performance and easy recovery still keeps a ...significant challenge. Herein, the novel ZIF-derived hierarchically porous carbon nanofibers (ZCNFs) were fabricated by electrospinning and calcination with ZIF-67 as the nanoparticles precursor and PAN as the CNFs precursor, and they were used as the supports of Pd nanoparticles for preparing the Pd@ZCNFs-x catalysts x is the mass ratio of ZIF-67 to PAN (%). Pd@ZCNFs-20 exhibits superior catalytic performance in the phenol hydrogenation to cyclohexanone, and its catalytic activity is 2.2 times higher than that of Pd@ZCNFs-0. The ZIF-67 doping is in favor of the formation of ZCNFs with more defects, larger surface area, hierarchical pore structure, higher N content and better Pd dispersion, thereby improving the catalytic activity. Furthermore, the as-prepared Pd@ZCNFs-20 catalyst is easy to be recovered from the reaction mixture due to its one-dimensional structure, and shows good reusability during six reaction cycles. In view of the high catalytic performance and reusability of the Pd@ZCNFs catalysts, the developed hybrid ZCNFs are potential candidates for the phenol hydrogenation.
Graphic Abstract
The ZIF-67 doping is in favor of the formation of ZIF-derived hierarchical porous carbon nanofibers (ZCNFs) with more defects, larger surface area, hierarchical pore structure, higher N content and better Pd dispersion, thereby improving the catalytic activity of Pd@ZCNFs in the phenol hydrogenation to cyclohexanone.
In this study, ZIF‐8 modified fluorinated graphene composite (FG@ZIF‐8) was innovatively prepared and used as a novel functional filler to improve the anticorrosion performance of epoxy coating on ...Q235 carbon steel. The morphology and structure of FG@ZIF‐8 composites were characterized by scanning electron microscopy (SEM), x‐ray powder diffractometer (XRD), Fourier transform infrared spectrometer (FT‐IR), and x‐ray photoelectron spectroscopy (XPS) tests. The results showed that the structure and morphology of the composites largely depended on the composition ratio of FG and ZIF‐8. The mechanical properties and corrosion resistance of FG@ZIF‐8 modified coatings were also investigated. The unique two‐dimensional sheet structure and insulation of FG in the FG@ZIF‐8 filler can not only inhibit the penetration of corrosive media but also discourage electron migration effectively on the interface of coating/matrix during the electrochemical reaction. Meanwhile, the chemical cross‐linking between the amine groups in ZIF‐8 and the epoxy group increases the degree of densification of the coatings. Besides, the 2‐methylimidazole from the dissolution of ZIF‐8 on FG@ZIF‐8 will also inhibit the corrosion reaction. These advantages endow the FG@ZIF‐8 modified epoxy coatings an excellent long‐term corrosion resistance. Our findings may inspire the development of new graphene‐based materials with superior protective properties for metallic materials.
