Zeolitic Imidazolate Framework Research Articles

Coembedding Fe Single Atom-Coupled MoC Nanoparticles in N-Doped Hierarchically Porous Carbon Cubes for Oxygen Electroreduction.

Promotion of oxygen reduction reaction (ORR) kinetics, to a large extent, depends on the rational modulation of the electronic structure and mass diffusion of electrocatalysts. Herein, a ferrocene (Fc)-assisted strategy is developed to prepare Fc-trapped ZnMo-hybrid zeolitic imidazolate framework (Fc@ZnMo-HZIF-50) and the derived Fe single atom coupling with MoC nanoparticles, coembedded in hierarchically porous N-doped carbon cubes (MoC@FeNC-50). The introduced Fc is utilized not only as an iron source for single atoms but also as a morphology regulator for generating a hierarchically porous structure. The redistribution of electrons between Fe single atoms and MoC nanoparticles effectively promotes the adsorption of O2 and the formation of *OOH intermediates during the ORR process. Along with a 3D hierarchically porous architecture for enhanced mass transport, the as-fabricated MoC@FeNC-50 presents excellent activity (E1/2 = 0.83 V) and durability (only 9.5% decay in current after 40000 s). This work could inspire valuable insights into the construction of efficient electrocatalysts through electron configuration and kinetics engineering.

Reactive Extrusion Printing of Zeolitic Imidazolate Framework Films.

An outstanding challenge for the field of metal-organic frameworks (MOFs) is structuring to form forms with greater useability. Reactive extrusion printing (REP) is a technique for the direct formation of films from their molecular components on-demand and on-location. Here we apply REP for the first time to zeolitic imidazolate frameworks (ZIFs) and study the interplay of solvent and molarity ratio on the phase distribution between ZIF-8 and ZIF-L in reactive printed films. Our results show that REP controllably directs phase formation between ZIF-L and ZIF-8 and that REP also gives control over crystal size and that high-quality ZIF-8 films, in particular, are produced in low-dispersity interconnected nanoparticulate form. Importantly, we show that REP is responsive to established surface-functionalization techniques to control important printing parameters of line width and thickness. This work expands the repertoire of REP to the important class of ZIFs.

Nanoengineering Multilength-Scale Porous Hierarchy in Mesoporous Metal-Organic Framework Single Crystals.

Developing a reliable method for constructing mesoporous metal-organic frameworks (MOFs) with single-crystalline forms remains a challenging task despite numerous efforts. This study presents a solvent-mediated assembly method for fabricating zeolitic imidazolate framework (ZIF) single-crystal nanoparticles with a well-defined micro-mesoporous structure using polystyrene-block-poly(ethylene oxide) diblock copolymer micelles as a soft-template. The precise control of particle sizes, ranging from 85 to 1200 nm, is achieved by regulating nucleation and crystal growth rates while maintaining consistent pore diameters in mesoporous nanoparticles and a rhombohedral dodecahedron morphology. Furthermore, this study presents a robust platform for nanoarchitecturing to prepare hierarchically porous materials (e.g., core-shell and hollow structures), including microporous ZIF@mesoporous ZIF, hollow mesoporous ZIF, and mesoporous ZIF@mesoporous ZIF. Such a multimodal pore design, ranging from microporous to microporous/mesoporous and further micro-/meso-/macroporous, provides significant evidence for the future possibility of the structural design of MOFs.

New Insights into ZIF-90 Synthesis

Zeolitic imidazolate frameworks (ZIFs) are traditionally synthesized using N, N-dimethylformamide (DMF). However, DMF is toxic and hazardous to human health and the environment, hence other alternative solvents need to be considered. Herein, three different solvents like methanol, water and acetone were used to replace DMF and to explore the syntheses of ZIF-90 using a conventional and a microwave-assisted solvothermal method to obtain hydrothermally stable products, which also exhibit an increased water uptake. Pure ZIF-90 was synthesized under ambient pressure at 60 °C for 90 min using the conventional solvothermal method in an acetone–water solution, while under microwave irradiation it was formed in only 5 min at 80 °C. Altering methanol, water and acetone in the reaction mixture significantly affected the structural and water adsorption properties of ZIF-90s, which were monitored via PXRD, TGA, nitrogen and water sorption, and SEM. The highly efficient, less toxic, low-cost and activation-free microwave synthesis resulted in the formation of ZIF-90 nanoparticles that exhibited the highest maximum water adsorption capacity (0.37 g/g) and the best hydrothermal stability between water adsorption at 30 °C and desorption at 100 °C at 12.5 mbar among all the products obtained.

Extent of Radiolytic Damage from Liquid Cell TEM Experiments on Metal-Organic Frameworks via Post-Mortem 4D-STEM.

We report a systematic analysis of electron beam damage of the zeolitic imidazolate framework (ZIF-8) during liquid cell transmission electron microscopy (LCTEM). Our analysis reveals ZIF-8 morphology is strongly affected by solvent used (water vs dimethylformamide), electron flux applied, and imaging mode (i.e., TEM vs STEM), while ZIF-8 crystallinity is primarily affected by accumulated electron fluence. Our observations indicate that the stability of ZIF-8 morphology is higher in dimethylformamide (DMF) than in water. However, in situ electron diffraction indicates that ZIF-8 nanocrystals lose crystallinity at critical fluence of ∼80 e-Å-2 independent of the presence of solvent. Furthermore, 4D-STEM analysis as a post-mortem method reveals the extent of electron beam damage beyond the imaging area and indicates that radiolytic reactions are more pronounced in TEM mode than in STEM mode. These results illustrate the significance of radiolysis occurring while imaging ZIF-8 and present a workflow for assessing damage in LCTEM experiments.

Monocyte/Macrophage-Mediated Transport of Dual-Drug ZIF Nanoplatforms Synergized with Programmed Cell Death Protein-1 Inhibitor Against Microsatellite-Stable Colorectal Cancer.

Microsatellite-stable colorectal cancer (MSS-CRC) exhibits resistance to programmed cell death protein-1 (PD-1) therapy. Improving the infiltration and tumor recognition of cytotoxic T-lymphocytes (CTLs) is a promising strategy, but it encounters huge challenges from drug delivery and mechanisms aspects. Here, a zeolitic imidazolate framework (ZIF) coated with apoptotic body membranes derived from MSS-CRC cells is engineered for the co-delivery of ginsenoside Rg1 (Rg1) and atractylenolide-I (Att) to MSS-CRC, named as Ab@Rg1/Att-ZIF. This system is selectively engulfed by Ly-6C+ monocytes during blood circulation and utilizes a "hitchhiking" mechanism to migrate toward the core of MSS-CRC. Ab@Rg1/Att-ZIF undergoes rapid disassembly in the tumor, released Rg1 promotes the processing and transportation of tumor antigens in dendritic cells (DCs), enhancing their maturation. Meanwhile, Att enhances the activity of the 26S proteasome complex in tumor cells, leading to increased expression of major histocompatibility complex class-I (MHC-I). These coordinated actions enhance the infiltration and recognition of CTLs in the center of MSS-CRC, significantly improving the tumor inhibition of PD-1 treatment from ≈5% to ≈69%. This innovative design, involving inflammation-guided precise drug co-delivery and a rational combination, achieves synergistic engineering of the tumor microenvironment, providing a novel strategy for successful PD-1 treatment of MSS-CRC.

Click-response-driven high-speed and ultrasensitive electrochemical sensing interface: Addressing its accuracy challenge

For electrochemical sensors, maintaining accuracy while achieving sensitive detection is of paramount importance. The fixation of the signal substance as one of the main steps in the construction process of a sensor has a significant impact on the accuracy. Currently, physical and chemical methods are the primary approaches for the fixation of the signal substance, which have the following issues. The accuracy of a sensor may be affected by the instability resulting from the physical immobilization of the signal substance and the chemical immobilization process is typically time-consuming. To overcome these obstacles, the ultra-sensitive electrochemical sensing interface is constructed by click reaction to achieve accurate and rapid detection of tumor biomarkers. After the formation of immune-sandwich structure in a test tube, a large amount of ethynylferrocene (EFc) molecules in the Zeolitic imidazolate frameworks (ZIF-8) immunoprobe are released under acidic conditions, followed by covalently linking to the substrate within 6 minutes through a click reaction. Under optimal conditions, the electrochemical sensor had an ultralow detection limit of 32.90 fg mL−1 for the model analyte (CEA) with a wide detection range from 100 fg mL−1 to 100 ng mL−1. This work provides a new perspective for designing electrochemical sensors with excellent performance.

Investigating solvent effects on synthesizing novel cobalt hydroxide and fluoride complex from Co(BF4)2 as active materials of the battery supercapacitor hybrid

Metal-organic framework (MOF) derivatives with tunable pore structure and improved conductivity are intensively designed as electroactive materials. Incorporating structure directing agents (SDA) is beneficial for designing MOF derivatives with excellent electrochemical performances. Ammonium fluoroborate has been reported as an effective SDA, coupled with cobalt salt and 2-methylimidazole, to synthesize zeolitic imidazolate framework-67 (ZIF-67) derivatives for charge storage. However, the synthetic environment for growing cobalt-based active materials is relatively complex. In this study, cobalt tetrafluoroborate (Co(BF4)2) is proposed as a novel cobalt precursor, supplementing cobalt ions and acting as the SDA in a single chemical, to synthesize the cobalt-based electroactive material of energy storage electrodes. Interactions between solvent molecules and solutes play significant roles on the morphology, composition, and electrochemical performance of active materials. Deionized water, methanol and ethanol are used as precursor solvents to understand their effects on material and electrochemical properties. The optimal electrode presents a specific capacitance of 608.3 F/g at 20 mV/s, attributed to the highest electrochemical surface area and evident compositions of cobalt fluoride and hydroxide. A battery supercapacitor hybrid achieves the maximum energy density of 45 Wh/kg at 429 W/kg. The CF retention of 100% and Coulombic efficiency of 99% are achieved after 10,000 cycles.

Rational construction of a hollow bimetallic porous composite derived zeolite imidazole framework based reduced graphene oxide nanosheets for supercapacitor applications

Rational construction of a hollow bimetallic porous composite derived zeolite imidazole framework based reduced graphene oxide nanosheets for supercapacitor applications

Fabrication of cobalt phosphide/nitride/carbon nanotube composite: An efficient bifunctional catalyst for hydrogen and oxygen evolution

Designing composites with rational structure and composition is a promising approach to obtain efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this study, zeolitic imidazolate frameworks-67 (ZIF-67) is employed as a self-sacrificing template to synthesize Co/carbon nanotubes (CNTs) precursor, which is subsequently in-situ nitrided and phosphorized to form cobalt phosphide/nitride/carbon nanotubes (Co2P/Co4N/CNTs) composite. The realized Co2P/Co4N composite exhibits heterogeneous nanoparticle microstucture with an average diameter of approximately 10 nm, encapsulated by carbon nanotubes with a porous dodecahedral array. Moreover, there is a well-defined interface between cobalt phosphide, cobalt nitride phases, and carbon nanotubes species. Benefiting from the synergistic effect of Co4N and Co2P, rich active sites, and high conductivity of CNTs, the composite catalyst demonstrates remarkable HER and OER activities, requiring overpotentials of 228 and 389 mV to support 100 mA cm−2 current density, respectively. This work presents a novel strategy for designing efficient bifunctional catalysts towards HER and OER.

Interface engineering strategy in bimetallic carbide and cobalt nanoparticles encapsulated in N-doped carbon nanotubes for excellent microwave absorption

In this paper, bimetallic Zn/Co zeolitic imidazole frameworks (Zn/Co-ZIFs) with various Zn/Co ratios have been successfully synthesized via a facile coprecipitation method, and then were converted into a series of N-doped bamboo-like carbon nanotubes (CNTs) encapsulated in Co nanoparticles with the aid of dicyandiamide after an annealing process. Results show that when the Zn/Co ratios in the Zn/Co-ZIF are 2:1 and 1:2, the morphology of ZIFs is hexagonal-star-like shape while it presents rod-like shape at the Zn/Co ratio of 1:1. The corresponding derivatives of these ZIFs after carbonization are identified as Co3ZnC/Co@CNTs, Co@CNTs-12, and Co@CNTs-11, and their microwave absorption performances are investigated at the same time. Among these as-synthesized composites, Co3ZnC/Co@CNTs exhibits the best microwave absorption behavior with a minimum reflection loss (RLmin) of −65.34 dB and an effective absorption bandwidth (EAB) of 5.35 GHz at a low filler content of 15 wt% and a thickness of 2.2 mm. Moreover, using CST to analyze Co3ZnC/Co@CNTs the radar cross section (RCS) was simulated, and the reduction value of RCS was −31.95 dB m2, and effective absorption can achieve full angle coverage. The outstanding microwave absorption capabilities of Co3ZnC/Co@CNTs can be credited to the effective impedance matching, robust interface polarization, and significant conduction loss. This paper also provides a strategy for strengthening the microwave absorption ability of absorbers through the interface engineering.

Interfacially crystallized Enzyme@MOFs biocatalytic membranes for highly efficient synthesis of D-amino acids via continuously recirculating stereoinversion

D-Amino acids (D-AAs) constitute essential building blocks found in many pharmaceuticals and fine chemicals. We herein presented the coating of polyvinylidene fluoride (PVDF) hollow fiber membrane with L-amino acid oxidase (LAAO) embedded zeolitic imidazolate framework-8 (ZIF-8) layer by a single-step interfacial biomineralization strategy for efficient synthesis of D-AAs. The ZIF-8 skeleton and PVDF membrane structure not only guaranteed free enzyme activity and stability, but also reinforced the applicability of this bioreactor for continuous enzymatic reactions. By placing the prepared biocatalytic membrane in the constructed circulation device, only the L-AAs can be specifically oxidized. The D-AAs are accumulated and synthesized after multiple rounds of continuously recirculating stereoinversion. Impressively, using tryptophan (Trp) as the model molecule, the thus-designed bioreactor exhibited an excellent conversion rate (92.10%) and ee% (99.41%) of D-Trp with a shorter time under constant flow conditions. This study provides an unprecedented protocol for highly efficient synthesis of D-AAs, and immensely advances the promising application field of membrane bioreactors.

Binary-Cooperative Ultrathin Porous Membrane for Gas Separation.

The construction of ultrathin porous membranes with stable structures is critical for achieving efficient gas separation. Inspired by the binary-cooperative structural features of bones and teeth-composed of rigid hydroxyapatite and flexible collagen, which confer excellent mechanical strength-a binary-cooperative porous membrane constructed with gel-state zeolitic imidazolate frameworks (g-ZIFs), synthesized using a metal-gel-induced strategy, is proposed. The enlarged cavity size and flexible frameworks of the g-ZIF nanoparticles significantly improve gas adsorption and diffusion, respectively. After thermal treatment, the coordination structures forming rigid segments in the g-ZIF membranes appear at the stacked g-ZIF boundaries, exhibiting a higher Young's modulus than the g-ZIF nanoparticles, denoted as the flexible segments. The g-ZIF membranes demonstrate excellent tensile and compression resistances, attributed to the effective translation of binary-cooperative effects of rigidity and flexibility into the membranes. The resulting dual-aperture structure, composed of g-ZIF nanoparticles surrounded by nanoscale apertures at the boundaries, yields a membrane with a stable CO2 permeance of 4834 GPU and CO2/CH4 selectivity of 90 within 3.0MPa.

Co–FeOOH thin nanosheets derived from 2D ZIF-L for efficient oxygen evolution reaction

The complicated reaction pathway and slow electron-transfer kinetics of the oxygen evolution reaction (OER) have been identified as a critical bottleneck that restricts the overall performance of electrochemical water splitting. Metal oxyhydroxides have emerged as viable alternative catalysts as compared to the precious metal-based commercial benchmarks. Yet, the activity may be compromised by the instability of the layered structures. Herein, a simple two-step method is developed for the synthesis of Co–FeOOH electrocatalysts by thermal treatment of cobalt-containing zeolitic imidazolate framework (ZIF-L) deposited on the skeleton of NF (nickel foam) in the presence of FeSO4 and urea. Co–FeOOH/NF, the thin nanosheet arrays exhibit a high specific surface area and high hydrophobicity. The addition of Co regulates the electronic environment around the Fe center, which optimizes the adsorption energy of intermediates and enhances the inherent OER activity of active sites. The Co–FeOOH nanoarrays show excellent OER performance and 99.7% Faradaic efficiency (FE). At current densities of 10 and 100 mA cm−2, there is a low overpotential of 208 and 249 mV, respectively at 1 M KOH. This kind of synthesis method will provide a promising approach for the construction of catalysts featuring stable structures for alkaline water oxidation.

Surface-enhanced Raman scattering nanotag of tunable ZIF-8 shell-encapsulated magnetic core-plasmonic satellites for disentangling chemical enhancement from electromagnetic enhancement

To enhance the stability of Raman reporters, these reporters were trapped in a metal organic framework (MOF) exoskeleton that was grown and compressed on Fe3O4@Au core–satellites, producing recyclable surface-enhanced Raman scattering (SERS) nanotags. Furthermore, encapsulation of Raman reporters in the assembled MOF-based nanocomposites was divided into two types of patterns, pre-enrichment and post-enrichment, in order to disentangle chemical enhancement of charge transfer (CT) from electromagnetic enhancement (EM) in SERS. Hence, to demonstrate the effect of encapsulation, a typical non-thiolated Raman reporter, for example crystal violet (CV) trapped in a core–satellite nanoassembly-based zeolitic imidazolate framework (ZIF-8) shell, was selected. The results suggest that stability and Raman intensity are remarkably improved. Moreover, the pattern of incorporation of CV into the ZIF-8 shell with tunable shell thickness can contribute to the disentangling of CT effects from EM effects.

Zeolitic imidazolate framework-8 as a high-affinity adsorbent for dispersive solid-phase extraction in the analysis of plant growth regulators in fruits.

Facile and sensitive determination of plant growth regulators (PGRs) in food samples is crucial but still poses a significant challenge. In this study, to enhance the sensitivity of the HPLC-DAD method for PGR detection, a dispersive solid phase extraction (d-SPE) method using zeolitic imidazolate framework-8 (ZIF-8) as the highly effective adsorbent is developed. ZIF-8 nanoparticles are formed through the coordination of Zn2+ with 2-methylimidazole. Due to its high porosity, large surface area, abundant π electronics and nitrogen electronics, ZIF-8 exhibits a strong affinity to PGRs due to the synergistic effects of π-π interaction, van der Waals force, H-bond, and surface effect. Under the optimal d-SPE conditions, the sensitivity of the method is significantly enhanced with outstanding performances, including a wide range of linearity (2.0-200 ng g-1) with high correlation coefficients (R ≥ 0.9989), low limits of detection (LODs, 0.9-8.0 ng g-1 for all PGRs), satisfactory precision (intra-day RSDs ≤ 3.3%, inter-day RSDs ≤ 4.2%), and high accuracy (recovery: 86.6-101.5%). The developed method was successfully applied to quantitatively detect 9 PGRs in fruit samples, yielding satisfactory results. This d-SPE-HPLC-DAD method, characterized by high sensitivity, simplicity, efficiency, ease of practice and cost-effectiveness for PGR detection, shows potential for detecting PGRs in other complex samples and provides a strategy for designing target-affinity adsorbents.

Upconversion-based chiral nanoprobe for highly selective dual-mode sensing and bioimaging of hydrogen sulfide in vitro and in vivo

Chiral assemblies have become one of the most active research areas due to their versatility, playing an increasingly important role in bio-detection, imaging and therapy. In this work, chiral UCNPs/CuxOS@ZIF nanoprobes are prepared by encapsulating upconversion nanoparticles (UCNPs) and CuxOS nanoparticles (NPs) into zeolitic imidazolate framework-8 (ZIF-8). The novel excited-state energy distribution-modulated upconversion nanostructure (NaYbF4@NaYF4: Yb, Er) is selected as the fluorescence source and energy donor for highly efficient fluorescence resonance energy transfer (FRET). CuxOS NP is employed as chiral source and energy acceptor to quench upconversion luminescence (UCL) and provide circular dichroism (CD) signal. Utilizing the natural adsorption and sorting advantages of ZIF-8, the designed nanoprobe can isolate the influence of other common disruptors, thus achieve ultra-sensitive and highly selective UCL/CD dual-mode quantification of H2S in aqueous solution and in living cells. Notably, the nanoprobe is also capable of in vivo intra-tumoral H2S tracking. Our work highlights the multifunctional properties of chiral nanocomposites in sensing and opens a new vision and idea for the preparation and application of chiral nanomaterials in biomedical and biological analysis.

Oriented growth of large-area metal-organic framework ZIF-8 membrane for hydrogen separation

Optimal orientation is the key factor to optimize the gas separation performance of metal-organic framework (MOF) membranes. However, it is still greatly challenging to prepare large-area oriented MOF membranes for industrial applications. Herein, we prepared compact and (100) oriented zeolitic-imidazolate framework-8 (ZIF-8) membranes with membrane area up to 500 cm2 on the graphite substrate via support-induced strategy within 2 h. With membrane thickness of only 620 nm, the (100) oriented ZIF-8 membranes exhibit high gas separation performances due to the reduction of inter-crystalline defects and permeation resistance. At 100 °C and 1 bar, the separation factors of H2/CO2, H2/CH4 and H2/C3H8 are 18.5, 58.2 and 101.6, respectively, with H2 permeance of about 160 x 10-9 mol·m-2·s-1·Pa-1. The different positions of the 500 cm2 ZIF-8 membrane show complete consistency in orientation and separation performance, recommending this membrane suitable for future industrial applications. Further, also oriented ZIF-67 and MOF-303 membranes can be consistently prepared by this strategy, confirming its versatility for the preparation of large-area MOF membranes.

Exploring the Economic Viability of Electrochemical Assessment for Water Contaminants with NiFe-PBA/ZIF-67 core shell Modified GCE

Zeolitic Imidazolate (metal organic) Frameworks (ZIFs) and Prussian Blue Analogues (PBAs) are promising materials in electrochemical sensing due to their unique properties. In this study, a composite material comprising NiFe-PBA and ZIF-67 was synthesized and made to form a uniform layer onto a glassy carbon electrode (GCE) to enhance electrochemical performance for furazolidone (FZD) detection. The synthesized NiFe-PBA/ZIF-67 composite exhibited excellent sensitivity, selectivity, and stability towards FZD detection, with a low limit of detection (LOD). The electrochemical behaviour of FZD on the NiFe-PBA/ZIF-67/GCE electrode was investigated, revealing a diffusion-controlled process. Differential pulse voltammetry (DPV) analysis demonstrated the synergetic effect of the PBA/MOF core-shell structure in enhancing FZD electro-reduction. The sensor exhibited exceptional LOD of 0.007 μM. Selectivity studies confirmed the sensor's ability to distinguish FZD from potential interferents. Extensive evaluations demonstrated the sensor's reproducibility, repeatability, and long-term stability, affirming its practical utility. Real sample analysis further validated the sensor's excellent analytical capabilities in diverse matrices.

Antimicrobial polymer-based zeolite imidazolate framework composite membranes for uranium extraction from wastewater and seawater

Extraction uranium (VI) (U(VI)) from wastewater and seawater is highly important for environmental protection and life safety, but it remains a great challenge. In this work, the growth of the zeolitic imidazolate framework-8 (ZIF-8) nanoparticles on the tannic acid (TA)-3-aminopropyltriethoxysilane (APTES) modified PVDF (TAP) membrane was designed to obtain an excellent U(VI) adsorbent. The zeolite imidazolate framework composite membrane (TAPP-ZIF-60) was prepared through polyethyleneimine (PEI) bridging strategy and temperature regulation strategy in solvothermal method. The coordination bond between PEI and ZIF-8 and the covalent bond between PEI and TAP are essential in forming stable composite membrane. TAPP-ZIF with different properties was synthesized through a temperature regulation process and the TAPP-ZIF prepared at 60 °C has the uniform morphology and good performance. The adsorption capacity of TAPP-ZIF-60 is 153.68 mg/g (C0 = 95.01 mg/L and pH = 8.0) and water permeability is 5459 L m−2 h−1 bar−1. After ten adsorption–desorption cycles, it is proved that TAPP-ZIF-60 has good repeatability and stability. In addition, the TAPP-ZIF-60 composites membrane has a good inhibitory effect on Staphylococcus aureus and Escherichia coli. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analysis reveal that the coordination between TAPP-ZIF-60 and uranyl ions is the primary factor contributing to the high adsorption capacity.