Growth Of Zeolitic Imidazolate Framework-8 Research Articles

ZIF-8@GO composites incorporated polydimethylsiloxane membrane with prominent separation performance for ethanol recovery

In this study, ZIF-8@GO composites with continuous inner channels for ethanol molecules were prepared by the in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles onto the surface of graphene oxide (GO) nanosheets, and filled into polydimethylsiloxane (PDMS) matrix to fabricate PDMS/ZIF-8@GO mixed matrix membranes (MMMs) for ethanol recovery via pervaporation. The as-prepared ZIF-8@GO composites and PDMS/ZIF-8@GO MMMs were characterized by various techniques. The results showed that ZIF-8 nanoparticles were uniformly dispersed on the surface of GO nanosheets and the hydrophobicity of ZIF-8@GO composites was stronger than GO due to the surface modification of GO by hydrophobic ZIF-8. Moreover, ZIF-8@GO composites as the filler not only exhibited the excellent compatibility with PDMS but also showed the good dispersion in PDMS matrix as compared to ZIF-8 nanoparticles. Therefore, ZIF-8@GO-based MMMs showed better separation performance than ZIF-8-based MMMs. The pervaporation performance of PDMS/ZIF-8@GO MMMs was studied by adjusting the filler type, particle loading, membrane thickness, and feed temperature. The optimized PDMS/ZIF-8@GO MMMs displayed a prominent separation factor of 22.2 with a total flux of 443.8 g/m2 h with 5 wt% ethanol aqueous solution at 40 °C, and therefore the superior pervaporation performance to most other PDMS-based MMMs. The excellent pervaporation results were attributed to the synergistic effect of GO nanosheet as a strong barrier and hydrophobic ZIF-8 nanoparticles with the continuous inner channels. The synergistic effect of hybrid particles may provide valuable guidance to the development of high-performance PDMS-based MMMs for pervaporation recovery of various organic compounds.

Efficient removal of formaldehyde with ZIF-8 growth on TiO2-coated activated carbon fiber felts prepared via atomic layer deposition

Zeolitic imidazolate framework-8 (ZIF-8) is regarded as an excellent adsorbent material for removing diverse toxic or hazardous gases. However, its milli- to nanoscale size typically restricts its applications. In this study, we demonstrate the ZIF-8 nanocrystals assembled on TiO2-coated activated carbon fiber felts via atomic layer deposition (ZIF-8@ALD-ACF felts), which can be used as a highly efficient adsorbent for HCHO removal. Using the TiO2-coated ACF felts as substrates via ALD can provide large number of growth sites for ZIF-8 nanocrystals, which results in fast and highly efficient removal of HCHO. Furthermore, ZIF-8@ALD-ACF felts achieve a highly efficient removal of HCHO under ultraviolet (UV) light. HCHO can be completely removed at high concentration within 110 min. Moreover, under UV light, it can be completely removed at low concentration within 6 min. The micropores in ACF and nanocages in ZIF-8 are suitable for small molecular HCHO uptaking and provide sufficient contact time for photocatalysis by TiO2. The ALD technology provides a useful methodology for the practical application of MOF-based materials.

Fabrication of multifunctional textiles with durable antibacterial property and efficient oil-water separation via in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on cotton fabric

Facile construction of multifunctional fabrics with durability still remains a challenge in the past decade. In this work, we report a facile fabrication of non-fluorinated superhydrophobic and antibacterial cotton fabric surfaces via in situ growing zeolitic imidazolate framework-8 (ZIF-8) nanocrystals on cotton fibers under room temperature condition and subsequently coating with polydimethylsiloxane (PDMS). The surface morphology and chemical composition of treated fabric have been characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). The as-prepared cotton fabric showed superhydrophobic property with a water contact angle (WCA) of 151.36° and a sliding angle of 3.6° and excellent antibacterial properties against E. coli and S. aureus. The durability of the superhydrophobic and antibacterial fabrics was evaluated by repeated washing and abrasion cycles. The as-prepared fabrics retained their excellent antibacterial property and superhydrophobicity after 300 cycles of abrasion and 5 cycles of washing. The robustness of superhydrophobicity and antibacterial activity made this method has wild application prospects in biomedical field in the future.

An enzyme-free electrochemical biosensor for simultaneous detection of two hemophilia A biomarkers: Combining target recycling with quantum dots-encapsulated metal-organic frameworks for signal amplification

A sensitive and selective electrochemical method for simultaneous detection of two hemophilia A-related microRNAs (miR-1246 and miR-4521) was developed. This detection tactic was based on gold nanoparticles (AuNPs), heavy metals quantum dots-encapsulated metal-organic frameworks (QDs@ZIF-8), and catalytic hairpin assembly (CHA) for signal application. Primarily, hairpins H1 and H2 were hybridized with targets miR-1246 (T1) and miR-4521 (T2) for forming H1-T1 and H2-T2 duplex stranded DNAs (dsDNAs) that were able to open the hairpins H3 and H4 for the formation of H1–H3 and H2–H4 dsDNAs. Meanwhile, lots of H1–H3 and H2–H4 dsDNAs were created by releasing the target to take part in the next cycle for signal amplification. And then single stranded fragments of H1–H3 and H2–H4 dsDNAs were utilized for hybridizing the PbS@ZIF-8-S1 and CdS@ZIF-8-S2 in order to amplify the electrochemical signal. The diagnosis of corresponding target miRs using differential pulse voltammetry has been possible by releasing Pb (II) and Cd (II) ions from PbS@ZIF-8 and CdS@ZIF-8 tags by HCI leaching. In this context, encapsulation of heavy metals quantum dots (QDs) was done in zeolitic imidazolate framework-8 (ZIF-8) to form QDs@ZIF-8 muti-core-shell particles by in situ growth of ZIF-8 in the presence of QDs. Since the quantity of QDs tagged to each target miRs grows massively, being resulted from a huge number of QDs that encapsulated in each QDs@ZIF-8 label, the sensitivity of the biosensor using QDs@ZIF-8 particles as signal tags is about 15 times that of a biosensor using QDs as signal tags. Several conditions of determination like incubation time for labeling and capture probe, HCl leaching time, and reaction time of CHA were optimized. Under the optimized conditions, this assay allowed the detection of target miRs in the range of 1 fM to 1 μM with detection limits of 0.19 fM and 0.28 fM for miR-1246 and miR-4521 (S/N = 3). The biosensor can discriminate complementary, 1-base mismatched and non-complementary sequences quite well, according to the catalytic hairpin assembly. Furthermore, the biosensor was utilized efficiently for quick and direct analysis of microRNAs in human serum. Thus, this tactic presents an innovative platform for microRNAs expression profiling in biomedical research and clinical diagnosis.

Highly Sensitive Detection of Dopamine at Ionic Liquid Functionalized RGO/ZIF-8 Nanocomposite-Modified Electrode

A hybrid and hierarchical nanocomposite was successfully prepared by the growth of zeolitic imidazolate framework-8 (ZIF-8) on the template of ionic liquid (IL, [Bmim][BF4]) functionalized reduced graphene oxide (IL-RGO). The structure and morphology of the IL-RGO/ZIF-8 nanocomposite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), and Raman spectroscopy. The results showed that RGO sheets were refrained from restacking by IL, and ZIF-8 nanoparticles grew well on the surface of IL-RGO. Owing to the synergistic effect from large surface area and excellent electrocatalytic activity of ZIF-8 and great electrical conductivity of IL-RGO, a highly sensitive sensor for dopamine (DA) can be obtained. IL-RGO/ZIF-8-modified electrode exhibits good electrocatalytic activity and electroconductive properties towards DA which were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Compared with bare or IL-RGO-modified electrodes, the IL-RGO/ZIF-8-modified electrode effectively depressed the oxidation overpotential of DA. The linear response range of DA was from 1.0×10−7 to 1.0×10−4 mol/L with a low detection of limit 3.5×10−8 mol/L. In addition, the sensor was shown to provide satisfactory stability for the determination of DA.

High Biocompatible ZIF-8 Coated by ZrO2 for Chemo-microwave Thermal Tumor Synergistic Therapy.

The zeolitic imidazolate framework-8 (ZIF-8) is a specifically promising drug carrier due to its excellent intrinsic properties. However, the high toxicity of ZIF-8 nanoparticles severely limits their further research and clinical application. In this work, the biocompatibility of ZIF-8 nanoparticles is greatly improved by coating ZrO2 onto the surface. The survival rate of cells and mice in the ZIF-8@ZrO2 nanocomposite group is significantly increased compared with the undecorated ZIF-8 nanoparticle group. Doxorubicin (DOX) as a chemotherapeutic drug is deposited during the ZIF-8 growth by a facile one-pot method. Ionic liquid (IL) is loaded into the pore of the ZIF-8/DOX@ZrO2 nanocomposites for enhancing microwave thermal therapy. The tumor inhibition rate of ZIF-8/DOX@ZrO2@IL nanocomposites with synergistic microwave thermal therapy and chemotherapy is obviously higher than in other groups. In addition, the ZIF-8/DOX@ZrO2@IL nanocomposites are used for real-time monitoring of the therapeutic outcomes due to the excellent computed tomography contrast agent, ZrO2. Therefore, such a ZrO2 coating strategy shows great promise for overcoming high toxicity of ZIF-8 nanoparticles, which offers a new platform for tumor synergistic microwave thermal therapy and chemotherapy using the ZIF-8/DOX@ZrO2@IL nanocomposite as a theranostic nanocarrier.

An electrochemical immunobiosensor for ultrasensitive detection of Escherichia coli O157:H7 using CdS quantum dots-encapsulated metal-organic frameworks as signal-amplifying tags

We report here cadmium sulfide quantum dots (CdS QDs)-encapsulated metal-organic frameworks as signal-amplifying tags for ultrasensitive electrochemical detection of Escherichia coli O157:H7 (E. coli O157:H7). CdS QDs were encapsulated in zeolitic imidazolate framework-8 (ZIF-8) to form CdS@ZIF-8 muti-core-shell particles by in situ growth of ZIF-8 in the presence of CdS QDs. To specifically recognize E. coli O157:H7 cells, CdS@ZIF-8 particles were coated with polyethyleneimine to introduce amino groups on their surfaces, followed by surface modification of anti-E. coli O157:H7 antibody. A sandwich-type electrochemical immunobiosensor for the detection of E. coli O157:H7 was fabricated using CdS@ZIF-8 particles as signal tags. Cd(II) ions were released from CdS@ZIF-8 tags by HCl leaching, enabling the detection of E. coli O157:H7 by differential pulse voltammetry. Under the optimized conditions, the linear range of the biosensor is from 10 to 108 colony forming units (CFU) per mL for E. coli O157:H7 detection, with the detection limit of 3 CFU mL−1 (S/N = 3). The sensitivity of the biosensor for E. coli O157:H7 detection using CdS@ZIF-8 particles as signal tags is 16 times that of a biosensor using CdS QDs as signal tags, because the number of CdS QDs labeled to each bacterial cell increases greatly resulting from a great number of CdS QDs encapsulated in each CdS@ZIF-8 label. This method was successfully used to detect E. coli O157:H7 in milk samples.

Facile synthesis of zeolitic imidazolate framework-8 (ZIF-8) by forming imidazole-based deep eutectic solvent

We report here the synthesis of ZIF-8 with “deep eutectic method”, a mild, efficient and environmentally friendly alternative to conventional synthesis that is carried out near room temperature, no organic solvent and at a stoichiometric molar ratio of zinc salt and imidazole. Deep eutectic method draws inspiration from the feasible formation of Deep eutectic solvent between quaternary ammonium salt and imidazole. The synthesis was performed by simply heating the mixtures of zinc salt, imidazole and quaternary ammonium salt, the hydrogen bond interaction between quaternary ammonium salt and 2-Mim could facilitate the deprotonation of 2-Mim, then promote the coordination between 2-Mim and Zn2+ and accelerate the nucleation and growth of ZIF-8. Particularly, the ZIF-8 synthesized by deep eutectic method possesses a co-existence of micropores and mesopores due to the template role of quaternary ammonium salt. Furthermore, The ZIF-8 synthesized by deep eutectic method exhibited higher capacity for the adsorption of CO2 than ZIF-8 prepared by conventional solution-based method due to its high surface area and large pore volume.

Metal-Organic-Framework-Derived N-Doped Hierarchically Porous Carbon Polyhedrons Anchored on Crumpled Graphene Balls as Efficient Selenium Hosts for High-Performance Lithium-Selenium Batteries.

Developing carbon scaffolds showing rational pore structures as cathode hosts is essential for achieving superior electrochemical performances of lithium-selenium (Li-Se) batteries. Hierarchically porous N-doped carbon polyhedrons anchored on crumpled graphene balls (NPC/CGBs) are synthesized by carbonizing a zeolitic imidazolate framework-8 (ZIF-8)/CGB composite precursor, producing an unprecedented effective host matrix for high-performance Li-Se batteries. Mesoporous CGBs obtained by one-pot spray pyrolysis are used as a highly conductive matrix for uniform polyhedral ZIF-8 growth. During carbonization, ZIF-8 polyhedrons on mesoporous CGBs are converted into N-doped carbon polyhedrons showing abundant micropores, forming a high-surface-area, high-pore-volume hierarchically porous NPC/CGB composite whose small unique pores effectively confine Se during melt diffusion, thereby providing conductive electron pathways. Thus, the integrated NPC/CGB-Se composite ensures high Se utilization originating from complete electrochemical reactions between Se and Li ions. The NPC/CGB-Se composite cathode exhibits high discharge capacities (998 and 462 mA h g-1 at the 1st and 1000th cycles, respectively, at a 0.5 C current density), good capacity retention (68%, calculated from the 3rd cycle), and excellent rate capability. A discharge capacity of 409 mA h g-1 is achieved even at an extremely high (15.0 C) current density.

Investigation of Controlled Growth of Metal-Organic Frameworks on Anisotropic Virus Particles.

Biomimetic mineralization with metal-organic frameworks (MOF), typically zeolitic imidazolate framework-8 (ZIF-8), is an emerging strategy to protect sensitive biological substances against denaturing environmental stressors such as heat and proteolytic agents. Additionally, this same biomimetic mineralization process has the potential of being used to create distinct core-shell architectures using genetically or chemically modified viral nanoparticles. Despite the proliferation of examples for ZIF-8 growth on biological or proteinaceous substrates, systematic studies of these processes are few and far between. Herein, we employed the tobacco mosaic virus (TMV) as a model biological template to investigate the biomimetic mineralization of ZIF-8, which has been proven to be a robust MOF for encasing and protecting inlaid biological substances. Our study shows a systematic dependence upon ZIF-8 crystallization parameters, e.g., ligand to metal molar ratio and metal concentration, which can yield several distinct morphologies of TMV@ZIF-8 composites and phases of ZIF-8. Further investigation using charged synthetic conjugates, time dependent growth analysis, and calorimetric analysis has shown that the TMV-Zn interaction plays a pivotal role in the final morphology of the TMV@ZIF-8, which can take the form of either core-shell bionanoparticles or large crystals of ZIF-8 with entrapped TMV located exclusively on the outer facets. The design rules outlined here, it is hoped, will provide guidance in biomimetic mineralization of MOFs on proteinaceous materials using ZIF-8.

Functionalization of cellulose fiber by in situ growth of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals for preparing a cellulose-based air filter with gas adsorption ability

The particulate matters (PMs) and toxic gases in air have resulted in serious impacts on public health. The development of “green” air filtering materials for isolating these pollutants is of vital importance. Here, we prepared a multi-functional cellulose-based air filter (CFs@ZIF-8 filter) by in situ growth of ZIF-8 nanocrystals on the surface of cellulose fibers. The incorporation of ZIF-8 nanocrystals increased the specific surface area of filter, strengthened the interactions between filter and PMs, and provided abundant cavities and gas adsorption sites for filter. The filtration efficiency of CFs@ZIF-8 filter for PM0.3 could reach to an ultrahigh level of 99.9%. The gas (nitrogen) adsorption capacity of CFs@ZIF-8 filter was 200 times higher than that of original cellulose-based filter (CFs-filter). The contributions of ZIF-8 on these surpassing properties of CFs@ZIF-8 filter were deeply analyzed. This study provided an effective strategy for developing “green” and multi-functional cellulose-based air filter.

Enhancing mechanical stability and uniformity of 2-D continuous ZIF-8 membranes by Zn(II)-doped polydopamine modification

Zeolitic imidazolate framework-8 (ZIF-8) with regular pore size (~ 0.34nm) is widely attempted for gas separation membranes based on size sieving. However, the prospect is subjected to fabricating the continuous ZIF-8 membranes with high mechanical stability and uniformity. In response, an adhesive layer of Zn(II)-doped polydopamine (Zn-PDA) is pre-coated on the stainless steel nets in this work to improve ZIF-8 nucleation and growth. Zn-PDA layer shows high tolerance to ultrasonic agitation and heated methanol (system for ZIF-8 synthesis), little dissolution within 24h, which supplies a high stable surface for ZIF-8 growth. Furthermore, the Zn(II) doped in PDA layer is opportunely serving as the even-distributed ZIF-8 nucleation starting sites, verified with the EDX and FE-SEM images for the aggregated Zn(II) clusters and the nascent ZIF-8 crystals. Therefore, an indented and hinged boundary is constructed between ZIF-8 and substrate to enhance the mechanical stability. The FE-SEM images after ultrasonic agitation show that the continuous ZIF-8 membranes prepared on Zn-PDA layers can tolerate the deformation to a certain extent. Finally, the prepared ZIF-8 membranes behave excellently with αH2/CO2 = 9.9, αH2/CO = 17.2, αH2/CH4 = 26.0, and permeation rate JH2 = 3980 GPU. This work supplied a useful approach to enhance mechanical stability and uniformity of defect-free ZIF-8 membranes.

Ultrasensitive Assay for Telomerase Activity via Self-Enhanced Electrochemiluminescent Ruthenium Complex Doped Metal-Organic Frameworks with High Emission Efficiency.

Here, an ultrasensitive "off-on" electrochemiluminescence (ECL) biosensor was proposed for the determination of telomerase activity by using a self-enhanced ruthenium polyethylenimine (Ru-PEI) complex doped zeolitic imidazolate framework-8 (Ru-PEI@ZIF-8) with high ECL efficiency as an ECL indicator and an enzyme-assisted DNA cycle amplification strategy. The Ru-PEI@ZIF-8 nanocomposites were synthesized by self-enhanced Ru-PEI complex doping during the growth of zeolitic imidazolate framework-8 (ZIF-8), which presented high ECL efficiency and excellent stability. Furthermore, owing to the porosity of Ru-PEI@ZIF-8, the self-enhanced Ru-PEI complex in the outer layer and inner layer of self-enhanced Ru-PEI@ZIF-8 could be excited by electrons causing the utilization ratio of the self-enhanced ECL materials to be remarkably increased. To further improve the sensitivity of the proposed biosensor, the telomerase activity signal was converted into the trigger DNA signal which was further amplified by an enzyme-assisted DNA recycle-amplification strategy. The proposed ECL biosensor presented great performance for telomerase activity detection from 5 × 101 to 106 Hela cells with a detection limit of 11 cells. Moreover, this method was applied in the detection of telomerase activity from cancer cells treated with an anticancer drug, which indicated the proposed method held potential application value as an evaluation tool in anticancer drug screening.

Hybridization of a Metal–Organic Framework with a Two-Dimensional Metal Oxide Nanosheet: Optimization of Functionality and Stability

An effective way to improve the functionalities and stabilities of metal–organic frameworks (MOFs) is developed by employing exfoliated metal oxide 2D nanosheets as matrix for immobilization. Crystal growth of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals on the surface of layered titanate nanosheets yields intimately coupled nanohybrids of ZIF-8-layered titanate. The resulting nanohybrids show much greater surface areas and larger pore volumes than do the pristine ZIF-8, leading to the remarkable improvement of the CO2 adsorption ability of MOF upon hybridization. Of prime importance is that the thermal- and hydrostabilities of ZIF-8 are significantly enhanced by a strong chemical interaction with the robust titanate nanosheet. A strong interfacial interaction between ZIF-8 and the layered titanate is verified by molecular mechanics simulations and spectroscopic analysis. The universal applicability of the present strategy for the coupling of MOFs and metal oxide nanosheets is substantiated by the stabilization of Ti-MOF-NH2 via the immobilization on exfoliated V2O5 nanosheets. The present study underscores that hybridization with metal oxide 2D nanosheets provides an efficient and universal synthetic route to novel MOF-based hybrid materials with enhanced gas adsorptivity and stability.

MOF Channels within Porous Polymer Film: Flexible, Self-Supporting ZIF-8 Poly(ether sulfone) Composite Membrane

Polymer - metal organic framework (MOF) composite membranes are promising materials for gas separation and could be potentially applied within many industrial applications. However, key limitations of currently reported layered MOF-polymer composites are their lack of scalability and mechanical stability. A big challenge for synthesis of such composites is directing the growth of homogeneous, defect-free MOF crystal layers. Here, a membrane synthesis method allowing the formation of flexible, noncontinuous zeolitic imidazolate framework 8 (ZIF-8) – poly(ether sulfone) (PES) composite membranes is presented. The ZIF-8 growth is restricted to the PES pores by exploiting directed ZnO seed-nanoparticles. The seeding process is part of the membrane formation process itself and allows for specifically integrating ZnO within polymeric membranes enabling easy and scalable control of the MOF-crystal formation. During solvent casting and membrane formation, a phase separation process allows trapping ZnO seed-nanopa...

Metal Oxide Assisted Preparation of Core-Shell Beads with Dense Metal-Organic Framework Coatings for the Enhanced Extraction of Organic Pollutants.

Dense and homogeneous metal-organic framework (MOF) coatings on functional bead surfaces are easily prepared by using intermediate sacrificial metal oxide coatings containing the metal precursor of the MOF. Polystyrene (PS) beads are coated with a ZnO layer to give ZnO@PS core-shell beads. The ZnO@PS beads are reactive in the presence of 2-methylimidazole to transform part of the ZnO coating into a porous zeolitic imidazolate framework-8 (ZIF-8) external shell positioned above the internal ZnO precursor shell. The obtained ZIF-8@ZnO@PS beads can be easily packed in column format for flow-through applications, such as the solid-phase extraction of trace priority-listed environmental pollutants. The prepared material shows an excellent permeance to flow when packed as a column to give high enrichment factors, facile regeneration, and excellent reusability for the extraction of the pollutant bisphenol A. It also shows an outstanding performance for the simultaneous enrichment of mixtures of endocrine disrupting chemicals (bisphenol A, 4-tert-octylphenol and 4-n-nonylphenol), facilitating their analysis when present at very low levels (<1 μg L(-1) ) in drinking waters. For the extraction of the pollutant bisphenol A, the prepared ZIF-8@ZnO@PS beads also show a superior extraction and preconcentration capacity to that of the PS beads used as precursors and the composite materials obtained by the direct growth of ZIF-8 on the surface of the PS beads in the absence of metal oxide intermediate coatings.