Zeolitic Imidazolate Framework Research Articles

Silk Fibroin Microneedles Loaded with Lipopolysaccharide-Pretreated Bone Marrow Mesenchymal Stem Cell-Derived Exosomes for Oral Ulcer Treatment.

Oral ulcers, superficial lesions on the surface of the oral mucosa, have a high incidence rate, and their main symptoms include local pain and erosion. Lipopolysaccharide (LPS)-preconditioned bone marrow mesenchymal stem cells and their secreted exosomes (LPS-pre-Exos) have been shown to promote recovery in various inflammatory conditions and wounds. However, studies documenting LPS-pre-Exos as a therapeutic intervention for oral mucosal-like diseases are lacking. In this study, we prepared a silk fibroin microneedle (MN) patch consisting of LPS-pre-Exos and zeolitic imidazolate framework-8 (ZIF-8) that localized at the tip and base, respectively, and used this MN patch for oral ulcer treatment. Upon insertion into the oral mucosa, continuous LPS-pre-Exos release was observed, which promoted macrophage polarization and tissue healing. Additionally, the ZIF-8 framework in the MN patch facilitated the controlled release of Zn2+, which demonstrated potent antimicrobial properties via synergistic effects. The in vitro experimental results showed that the silk fibroin MN patch can continuously release LPS-pre-Exos and Zn2+ for more than 7 days. Thus, the LPS-pre-Exos and ZIF-8-loaded silk fibroin MN patch exhibited good anti-inflammatory and antibacterial properties, promoting oral ulcer healing, and showed good histocompatibility. Hence, it may represent a potentially valuable strategy for facilitating oral ulcer healing.

Fabrication of a Stable and Highly Effective Anode Material for Li-Ion/Na-Ion Batteries Utilizing ZIF-12.

Transition metal selenides (TMSs) are receiving considerable interest as improved anode materials for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) due to their considerable theoretical capacity and excellent redox reversibility. Herein, ZIF-12 (zeolitic imidazolate framework) structure is used for the synthesis of Cu2Se/Co3Se4@NPC anode material by pyrolysis of ZIF-12/Se mixture. When Cu2Se/Co3Se4@NPC composite is utilized as an anode electrode material in LIB and SIB half cells, the material demonstrates excellent electrochemical performance and remarkable cycle stability with retaining high capacities. In LIB and SIB half cells, the Cu2Se/Co3Se4@NPC anode material shows the ultralong lifespan at 2000 mAg-1, retaining a capacity of 543 mAhg-1 after 750 cycles, and retaining a capacity of 251 mAhg-1 after 200 cycles at 100 mAg-1, respectively. The porous structure of the Cu2Se/Co3Se4@NPC anode material can not only effectively tolerate the volume expansion of the electrode during discharging and charging, but also facilitate the penetration of electrolyte and efficiently prevents the clustering of active particles. In situ X-ray difraction (XRD) analysis results reveal the high potential of Cu2Se/Co3Se4@NPC composite in building efficient LIBs and SIBs due to reversible conversion reactions of Cu2Se/Co3Se4@NPC for lithium-ion and sodium-ion storage.

Zeolitic imidazolate framework-8@polydopamine decorated carboxylated chitosan hydrogel with photocatalytic and photothermal antibacterial activity for infected wound healing

Open wounds are susceptible to bacterial infections, and antibiotics are commonly used to treat these infections. However, widespread use of antibiotics will easily induce bacterial resistance. Green antibacterial agents serve as excellent alternative for antibiotics in infection therapy. In this work, polydopamine (PDA) was used to modify the surface of ZIF-8, which not only enhances the water stability of Zeolitic imidazolate framework-8(ZIF-8) but also improves its photocatalytic and photothermal capabilities. ZIF-8@PDA was incorporated into carboxylated chitosan (CCS) films as an antibacterial agent, the resulting ZIF-8@PDA-CCS films exhibit excellent ionic/photocatalytic/photothermal antibacterial performance. The film exhibited an impressive 99% in vitro bacterial inhibition rate. After treatment with ZIF-8@PDA-CCS, the bacteria in infected wounds can be completely suppressed. These findings suggest that ZIF-8@PDA-CCS could serve as a potentional antibacterial dressing.

Fabrication of Highly Efficient ZIF-8@PEI Monoliths for CO2 Capture Using Phosphorylated Cellulose Nanofiber as a Binder.

This study involves the synthesis and comparison of zeolitic imidazolate frameworks (ZIFs), specifically ZIF-8 and ZIF-67 pristine with a commercial zeolite, emphasizing their CO2 affinity and sorption capability. To overcome challenges persisting in the handling and integration of these materials into industrial adsorption processes, particularly when limited to microcrystalline fine powders, we present herein an innovative manufacturing method to produce standalone monolithic supports. This process involves pseudoplastic paste formulations utilizing polyethylenimine (PEI) as a coagulant and locally fabricated phosphorylated cellulose nanofiber (PCNF) as a binding agent. Rheological investigation was conducted to anticipate the required shaping and design by means of paste flowability, consistency, and stiffness. XRD and FTIR results confirm the preservation of crystalline structure and the occurrence of amine functionalization associated with the presence of PEI, respectively. The proposed method significantly enhances the CO2 adsorption performance of the produced ZIF-8 monolith in comparison with that reached when using the pristine material, achieving a capacity of 1.25-2 mmol·g-1 at 30 °C under dry conditions in a pressure range of 1-13 bar, respectively. In other words, this work clearly highlights an effective applicability of the ZIF-8 monolith as an innovative sorbent for further designing CO2 capture industrial setups.

Confinement-Induced Biocatalytic Activity Enhancement of Light- and Thermoresponsive Polymer@Enzyme@MOF Composites.

Metal-organic frameworks (MOFs) are favorable hosting materials for fixing enzymes to construct enzyme@MOF composites and to expand the applications of biocatalysts. However, the rigid structure of MOFs without tunable hollow voids and a confinement effect often limits their catalytic activities. Taking advantage of the smart soft polymers to overcome the limitation, herein, a protection protocol to encapsulate the enzyme in zeolitic imidazolate framework-8 (ZIF-8) was developed using a glutathione-sensitive liposome (L) as a soft template. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were first anchored on a light- and thermoresponsive porous poly(styrene-maleic anhydride-N,N-dimethylaminoethyl methacrylate-spiropyran) membrane (PSMDSP) to produce PSMDSP@GOx-HRP, which could provide a confinement effect by switching the UV irradiation or varying the temperature. Afterward, embedding PSMDSP@GOx-HRP in L and encapsulating PSMDSP@GOx-HRP@L into hollow ZIF-8 (HZIF-8) to form PSMDSP@GOx-HRP@HZIF-8 composites were performed, which proceeded during the crystallization of the framework following the removal of L by adding glutathione. Impressively, the biocatalytic activity of the composites was 4.45-fold higher than that of the free enzyme under UV irradiation at 47 °C, which could benefit from the confinement effect of PSMDSP and the conformational freedom of the enzyme in HZIF-8. The proposed composites contributed to the protection of the enzyme against harsh conditions and exhibited superior stability. Furthermore, a colorimetric assay based on the composites for the detection of serum glucose was established with a linearity range of 0.05-5.0 mM, and the calculated LOD value was 0.001 mM in a cascade reaction system. This work provides a universal design idea and a versatile technique to immobilize enzymes on soft polymer membranes that can be encapsulated in porous rigid MOF-hosts. It also holds potential for the development of smart polymer@enzyme@HMOFs biocatalysts with a tunable confinement effect and high catalytic performance.

A Structural Mimic of Carbonic Anhydrase in Zeolitic Imidazolate Frameworks via Trans-functionalization for Enhancing Hydrolytic Activity.

Metal-organic frameworks (MOFs) have been widely considered as ideal platforms for the preparation of biomimetic catalysts, but it remains challenging to fabricate MOF-based enzyme-like catalysts with optimal activity. Here, we leverage the inherent flexibility of MOFs and propose a novel trans-functionalization strategy to construct a carbonic anhydrase (CA) mimic by the structural transformation from ZIF-L to ZIF-8. Theoretical and experimental results reveal that during the structural transformation, the hydroxyl group will preferentially coordinate with the interlayer Zn clusters to form the CA-like active center Zn-N3-OH. Therefore, more accessible active centers are generated on the as-prepared ZIF-8-OH, resulting in substantially enhanced catalytic activity in the hydrolysis of para-nitrophenyl acetate.

ZIF-8-derived nanocarbon composite-based highly active platinum group metal-free bimetallic electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Non-precious metal catalysts are ideal low-cost substitutes of Pt/C for the sluggish oxygen reduction reaction (ORR), despite the serious stability challenges in proton exchange membrane fuel cells (PEMFC) to alleviate the energy crisis and environmental problems. Platinum group metal (PGM)-free bimetallic composite electrocatalysts are assumed to be an interesting route to be investigated to address the stability and ORR selectivity related issues in PEMFC conditions. In this regard, we propose a simple and facile synthesis route by a composite of multi-walled carbon nanotubes and zeolitic imidazolate framework (ZIF)-8 followed by impregnating dual transition metals (FeMn, FeCo, and CoMn) and evaluate their ORR activity in acid media and PEMFC performance. Various catalyst materials are prepared and optimized to achieve the highest electrocatalytic performance. The prepared catalysts are characterized by various physico-chemical methods to elucidate their textural, structural, and morphological properties. The high ORR electrocatalytic activity and selectivity of the catalyst are reported in terms of half-wave potential and low H2O2 yield as determined by the rotating ring-disk electrode method. The significant electrochemical stability under accelerated durability test and high peak power density (787 mW cm−2) in H2-O2 PEMFC made these catalysts as potential candidates for efficient alternatives to PGMs in the fuel cell cathodes.

High-Entropy Metal Nitride Embedded in Concave Porous Carbon Enabling Polysulfide Conversion in Lithium-Sulfur Batteries.

The practical implementation of lithium-sulfur batteries is severely hindered by the rapid capacity fading due to the solubility of the intermediate lithium polysulfides (LiPSs) and the sluggish redox kinetics. Herein, high-entropy metal nitride nanocrystals (HEMN) embedded within nitrogen-doped concave porous carbon (N-CPC) polyhedra are rationally designed as a sulfur host via a facile zeolitic imidazolate framework (ZIF)-driven adsorption-nitridation process toward this challenge. The configuration of high-entropy with incorporated metal manganese (Mn) and chromium (Cr)will optimize the d-band center of active sites with more electrons occupied in antibonding orbitals, thus promoting the adsorption and catalytic conversion of LiPSs. While the concave porous carbon not only accommodates the volume change upon the cycling processes but also physically confines and exposes active sites for accelerated sulfur redox reactions. As a result, the resultant HEMN/N-CPC composites-based sulfur cathode can deliver a high specific capacity of 1274 mAh g-1 at 0.2C and a low capacity decay rate of 0.044% after 1000 cycles at 1C. Moreover, upon sulfur loading of 5.0mg cm-2, the areal capacity of 5.0mAhcm-2 can still be achieved. The present work may provide a new avenue for the design of high-performance cathodes in Li-S batteries.

MOFs meet wood with enlarged pores: A high-capacity and efficient removal of ciprofloxacin from water

The abuse of ciprofloxacin (CIP) has caused considerable worry because it not only seriously contaminates the environment but also endangers the ecology. Thus, effective antibiotic wastewater treatment technologies should be explored. In this paper, Hypericum residues were first pretreated with acidic deep eutectic solvents (DES) to remove lignin and hemicellulose (DH1 and DH2). Then, zeolite imidazolate frameworks (ZIF-8 and ZIF-67) were loaded on the wood to obtain four composites (collectively referred to as DH/ZIF), which were used for CIP removal from wastewater. The enlarged pore size of the wood's provided sufficient attachment sites for ZIF-8 and ZIF-67, which facilitated the efficient adsorption of CIP by the composites. The adsorption of CIP by all four composites (DH1/ZIF-8, DH2/ZIF-8, DH1/ZIF-67, DH2/ZIF-67) was above 1400 mg/g. The results of characterization, data fitting and parameterization suggest that pore filling, hydrogen bonding, electrostatic interactions and π-π stacking are the main mechanisms of CIP adsorption. In summary, DESs show great potential and broad utility in modifying waste biomass and compounding it with MOF to remove antibiotic contaminants.

π-d Interaction to promote Zn ion de-solvation and transference toward high-performance Zn-MnO2 battery

Aqueous zinc ion batteries (AZIBs) are one class of high-safety and low-cost electrochemical energy storage devices supplementary to the current lithium ion technologies. However, their cycling performance has been severely tethered by the high de-solvation barrier of hydrated Zn ions and uncontrolled dendrite growth and side reactions on the Zn anodes. Herein, an artificial zincophilic passivation layer is constructed on the Zn anode surface by impregnating the porous Zn-based zeolitic imidazole frameworks (ZIF-8) with polypyrrole of rich π-electron donation. This not only lowers the de-solvation and nucleation barriers through π-d interaction, but also offers spatial room for accommodating 3D matrix Zn storage, lending smooth Zn plating/stripping with greatly improved kinetics in addition to inhibited dendrite formation and side reactions. Consequently, at 5 mA cm−2 the as-modified Zn anodes demonstrate a high CE of 99.6 % for more than 1500 cycles in half-cells and a stable operation for more than 2500 h in symmetrical cells. The aqueous Zn-MnO2 full cells further present a superb cycling performance with a capacity retention of 86.3 % after 1200 cycles at 1 A g−1. This work underscores the application of zincophilic and porous passivation layer to mediate smooth Zn plating/stripping by modulating the de-solvation and nucleation energy barriers.

Hierarchically porous and single Zn atom-embedded carbon molecular sieves for H2 separations

Hierarchically porous materials containing sub-nm ultramicropores with molecular sieving abilities and microcavities with high gas diffusivity may realize energy-efficient membranes for gas separations. However, rationally designing and constructing such pores into large-area membranes enabling efficient H2 separations remains challenging. Here, we report the synthesis and utilization of hybrid carbon molecular sieve membranes with well-controlled nano- and micro-pores and single zinc atoms and clusters well-dispersed inside the nanopores via the carbonization of supramolecular mixed matrix materials containing amorphous and crystalline zeolitic imidazolate frameworks. Carbonization temperature is used to fine-tune pore sizes, achieving ultrahigh selectivity for H2/CO2 (130), H2/CH4 (2900), H2/N2 (880), and H2/C2H6 (7900) with stability against water vapor and physical aging during a continuous 120-h test.

Novel ZIFs nanostructures electro-engineered at carbon fiber for the highly sensitive and selective detection of isoeugenol.

Novel zeolitic imidazolate frameworks (ZIFs), classical subtypes of metal organic frameworks (MOFs), and nanostructures are electro-engineered onto carbon fiber (CF), leading to a unique freestanding electrochemical platform of budlike nano Zn-ZIFs decorated CF (BN-Zn-ZIFs/CF). The unique morphology, structure, and composition are characterized by electron microscopy and energy spectrum analysis. Notably, the BN-Zn-ZIFs/CF platform displays superb electrocatalysis towards the oxidation of isoeugenol with encouragingly low overpotential and high current response. The strong electrocatalytic oxidation capability of BN-Zn-ZIFs/CF makes it an excellent sensing platform for isoeugenol detection. BN-Zn-ZIFs/CF sensor exhibits high-performance isoeugenol sensing with an extremely low limit of detection (13nM) and wide detection range (0.1-700µM). Besides, the BN-Zn-ZIFs/CF sensor can greatly resist interference from common ions, major biomolecules, and some amino acids. Moreover, excellent reliability, stability, and practicality are obtained. Our work demonstrates that the as-prepared BN-Zn-ZIFs/CF can act as an high-performance electrochemical sensor for the isoeugenol detection, the well-developed ZIF nanocrystal-modified conductive substrates can be a unique platform for the efficient sensing of other molecules, and the electrochemical engineering strategy can be an effective method for the growing of fresh MOF nanocrystals at conductive substrates in various electrochemical applications.

Loofah sponge immobilized ZIF-8 for efficient adsorption removal of U (VI)

Efficient removal of radioactive and toxic uranium (U) from wastewater is highly desired. In this work, a novel adsorbent was prepared via in situ introducing zeolitic imidazolate framework-8 (ZIF-8) onto the hydrolyzed biomass loofah sponge (HLS) for the removal of U (VI). Benefiting from the introduction of ZIF-8, the physical and chemical properties of the composite adsorbent were significantly improved, leading to an enhanced U (VI) adsorption capacity. The results show that the maximum adsorption capacity of the adsorbent toward U (VI) is 244.03 mg/g under the optimal conditions. The adsorption kinetic parameters and isotherm of U (VI) well follow the pseudo second order model and Langmuir model, respectively. Besides, the thermodynamic parameters shows that the adsorption process of U (VI) is a spontaneous process with an exothermic nature. More importantly, the prepared adsorbent has a good reuseability and anti-interference capability during the adsorption of U (VI). This work supplies a new routine to design highly performed adsorbents for the removal of U (VI).

Synergistic effect of iron phthalocyanine and ultrafine cobalt nanoparticles for efficient CO2 electroreduction to syngas

Developing efficient electrocatalysts for CO2 electroreduction to syngas with a specific H2/CO ratio over a wide potential window is desperately required but still challenging. In this work, a series of dual-site catalysts composed of iron phthalocyanine (FePc) and ∼18 nm Cobalt nanoparticles (Co NPs) anchored on N-doped carbon matrix has been constructed from zeolitic imidazolate framework-67 (ZIF-67). Benefiting from the synergistic effect of FePc and Co NPs, the derived FePc/Co@N–C catalyst shows impressive capability for CO2 electrolysis to syngas. By varying the pyrolysis temperatures (600–800 °C) of ZIF-67 and the mass ratio of Co@N–C to FePc (1–3), an adjustable H2/CO ratio of 2–4 is obtained, and the value can be maintained stable within a potential window of −0.66 to −0.86 V vs. RHE in an H-type cell. Moreover, this electrocatalyst exhibits favorable stability without distinct performance decay. When conducted in a flow cell, an enhanced catalytic activity is demonstrated with an industrial current density (>100 mA cm−2) at −0.8 V vs. RHE and a steady H2/CO ratio of 2 from −0.4 to −0.6 V vs. RHE. This work provides a promising strategy of designing bifunctional electrocatalysts for syngas generation with stable H2/CO ratio across a wide potential range.

Highly efficient Zn-MOF derived Carbon-Nitrogen material based catalyst for nitroaromatic Hydrogenation: The role of Zn-O-C bond and Pyridinic-N

Zn-based catalysts have great feature of environmental friendliness and developmental potential to replace precious metals in heterogeneous catalytic hydrogenation. In this work, a porous CN material-based catalysts containing trace Zn were prepared by high-temperature pyrolysis using zeolitic imidazolate framework (ZIF-8) material as precursor. The result shows that (Zn)NC-800 and (Zn)NC-600–700 exhibit outstanding hydrogenation ability and good stability in nitro compounds hydrogenation reaction. Based on the results of characterization and DFT calculations, two hydrogenation active sites complete the hydrogenation of nitro compounds in (Zn)NC-800 and (Zn)NC-600–700: the residual trace Zn in the form of Zn-O-C bond can activate the CN structure and promote the conversion of nitrobenzene; the pyridinic-N is confirmed to accelerate the electron transfer and enhance the selectivity to aniline. This work has an enlightening significance for the efficient development of heterogeneous catalytic hydrogenation catalysts.

ZIF-derived "cocoon"-like in-situ Zn/N-doped carbon as high-capacity anodes for Li/Na-ion batteries

Owing to the unique structure and physicochemical properties, including high specific surface area, self-doped N atoms, open pore structure and good chemical stability, zeolitic imidazolate frameworks (ZIFs) and their derivatives have been widely used in the field of energy storage. Here, a new type of "cocoon"-like Zn/N doped ZIF-derived porous carbon (Zn@N-C-800) is synthesized as an anode for lithium-ion batteries (LIBs) and sodium ion batteries (SIBs) through a one-step carbonization process using a novel Zn-ZIF as the precursor. In Zn@N-C-800, the "cocoon"-like disordered carbon skeleton is conducive to electrolyte infiltration, while the Zn/N doping can provide additional active sites for ion storage. Benefiting from these unique structural characteristics, Zn@N-C-800 achieves excellent electrochemical performances as anode for both LIBs and SIBs: an ultrahigh rate capability of 352 mAh g−1 can be delivered at 12.8 A g−1 for LIBs; an outstanding long-term cycling stability (312 mAh g−1 at 1 A g−1 after 2000 cycles) can be achieved for SIBs. This paper provides new ideas for the design and preparation of high-performance anodes for LIBs and SIBs.

Harnessing the Synergy of ZIF‐67 Derived Nanohybrid‐Based Immunosensing for sensitive Detection of Helicobacter pylori

AbstractDetection of Helicobacter pylori (H. pylori) infection, a significant risk factor for chronic gastritis, peptic ulcers, and gastric adenocarcinoma, poses a formidable challenge due to the lack of sensitive and selective sensing platforms. Herein, we report the synthesis of a zeolitic imidazolate framework‐67 (ZIF‐67) derived Co/Co3O4/C (CoNH) porous nanostructure, optimized for the electrochemical immunosensing of H. pylori‐specific antigen VacA. By calcining ZIF‐67 at elevated temperatures, we obtained CoNH with enhanced electroactivity and conductivity, crucial for signal enhancement. The synthesized CoNH was thoroughly characterized using SEM, TEM, XPS, Raman, and FT‐IR techniques. Further signal amplification was achieved by introducing gold nanoparticles (AuNPs) onto CoNH‐modified screen‐printed carbon electrodes. Systematic investigation at each modification stage led to an optimized immunosensing platform with high sensitivity and selectivity for VacA detection. The developed immunosensor demonstrated the capability to detect low concentrations of VacA (0.1 ng/ml) within a wide linear range (0.1–50 ng/ml) with long‐term stability. This highly sensitive and selective biosensor holds promise for early‐stage diagnosis of H. pylori infection and gastric cancer.

A Self-Cascade Oxygen-Generating Nanomedicine for Multimodal Tumor Therapy.

Natural and artificial enzyme oxygen-generating systems for photodynamic therapy (PDT) are developed for tumor treatment, yet they have fallen short of the desired efficacy. Moreover, both the enzymes and photosensitizers usually need carriers for efficient delivery to tumor sites. Here, a self-cascade-enhanced multimodal tumor therapy is developed by ingeniously integrating self-cascade-enhanced PDT with Zn2+-overloading therapy. Manganese-porphyrin (TCPP-Mn) is chosen both as the photosensitizer and catalase (CAT) mimic, which can be encapsulated within glucose oxidase (GOx). Acid-responsive zeolitic imidazolate framework-8 (ZIF-8) is applied as the carrier for TCPP-Mn@GOx (T@G), attaining TCPP-Mn@GOx@ZIF-8 (T@G@Z). T@G@Z demonstrates robust anti-tumor ability as follows: upon the structural degradation of ZIF-8, GOx can mediate the oxidation of glucose and generate hydrogen peroxide (H2O2); TCPP-Mn can catalyze H2O2 into O2 for self-cascade-enhanced PDT; meanwhile, the released Zn2+ can enhance oxidative stress and induce mitochondrial dysfunction by destroying mitochondrial membrane potential; furthermore, immunotherapy can be activated to resist primary tumor and tumor metastasis. The self-cascade-enhanced T@G@Z exhibited its potential application for further tumor management.

Improvement of optical and structural properties of ZIF-8 by producing multifunctional Zn/Co bimetallic ZIFs for wastewater treatment from copper ions and dye

In the paper, high specific surface area (SSA) mono and bimetallic zeolitic imidazolate frameworks (ZIFs) based on zinc and cobalt metals are successfully synthesized at room temperature using different ratios of Zn to Co salts as precursors and ammonium as a solvent to tailor the properties of the produced ZIF and optimize the efficiency of the particles in water treatment from dye and copper ions, simultaneously. The results declare that monometallic and bimetallic ZIF microparticles are formed using ammonium and the tuning of pore sizes and also increasing the SSA by inserting the Co ions in Zn-ZIF particles is accessible. It leads to a significant increase in the thermal stability of bimetallic Zn/Co-ZIF and the appearance of an absorption band in the visible region due to the existence of Co in the bimetallic structures. The bandgap energies of bimetallic ZIFs are close to that of the monometallic Co-ZIF-8, indicating controlling the bandgap by Co ZIF. Furthermore, the ZIFs samples are applied for water treatment from copper ions (10 and 184 ppm) and methylene blue (10 ppm) under visible irradiation and the optimized multifunctional bimetallic Zn/Co ZIF is introduced as an admirable candidate for water treatment even in acidic conditions.

Polypyrrole wrapped‐carbon nanotube composites with self‐assembled core‐shell structure for high‐performance flexible supercapacitors

AbstractThe polypyrrole wrapped‐carbon nanotube composites with the core‐shell design are prepared via two‐step self‐assembly originated from the multi‐interactions of dopant, zeolitic imidazolate framework, carbon nanotube and pyrrole. The core composed of carbon nanotube effectively improves the conductivity of the composite and provides stable double‐layer capacitance. The shell composed of polypyrrole and tightly wrapped on carbon nanotubes effectively prevents the volume expansion of polypyrrole while undergoing the process of doping/de‐doping as well as endows supercapacitors with high pseudocapacitance. The polypyrrole‐coated carbon nanotube displays a remarkable specific capacitance of 510 F g−1 when operating at a current density of 1 A g−1. Surprisingly, the assembled polypyrrole wrapped‐carbon nanotube//activated carbon asymmetric supercapacitor not only possesses a high capacitance preservation of 88.5% after 10,000 charge/discharge cycles at 5 A g−1, but also shows superior flexibility and stable electrochemical behaviors when subjected to various bending angles. Furthermore, the flexible polypyrrole wrapped‐carbon nanotube//activated carbon supercapacitor achieves the superb energy density of 86.3 Wh kg−1 and the power density of 800 W kg−1 when operating at 1 A g−1. These results highlight the significant potential of this new generation of flexible supercapacitor devices.Highlights Polypyrrole is wrapped on carbon nanotube to form a core‐shell structure CNTs improve the conductivity and provides double‐layer capacitance The core‐shell design prevents the volume expansion of polypyrrole The assembled asymmetric supercapacitor shows superior flexibility