Zeolitic Imidazolate Framework Research Articles

Enhancing Electrocatalytic Kinetics via Synergy of Co Nanoparticles and Co/Ni-N4-C- and N-Doped Porous Carbon.

Transition-metal species embedded in carbon have sparked intense interest in the fields of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, improvement of the electrocatalytic kinetics remains a challenge caused by the synergistic assembly. Here, we propose a biochemical strategy to fabricate the Co nanoparticles (NPs) and Co/Ni-N4-C co-embedded N-doped porous carbon (CoNPs&Co/Ni-N4-C@NC) catalysts via constructing the zeolitic imidazolate framework (ZIF)@yeast precursor. The rich amino groups provide the possibility for the anchorage of Co2+/Ni2+ ions as well as the construction of Co/Ni-ZIF@yeast through the yeast cell biomineralization effect. The functional design induces the formation of CoNPs and Co/Ni-N4-C sites in N-doped carbon as well as regulates the porosity for exposing such sites. Synergy of CoNPs, Co/Ni-N4-C, and porous N-doped carbon delivered excellent electrocatalytic kinetics (the ORR Tafel slope of 76.3 mV dec-1 and the OER Tafel slope of 80.4 mV dec-1) and a high voltage of 1.15 V at 10 mA cm-2 for the discharge process in zinc air batteries. It provides an effective strategy to fabricate high-performance catalysts.

Incorporating Fluorescent Organosilica and Zeolitic Imidazolate Frameworks into Periodic Mesoporous Organosilica for the Enhanced Cargo Delivery of 5‐Fluorouracil

AbstractNanosized zeolitic imidazolate frameworks (nZIFs) are being researched as 5‐fluorouracil (5‐FU) carriers for the treatment of cancer. The surface functionalization of ZIFs with periodic mesoporous organosilicas (PMOs) is expected to enhance stability and prevent the flocculation of nZIFs. In this study, ZIF‐7 nanomaterials and fluorescent organosilicas (FITC−APTES) were effectively introduced into PMO nanoparticles, and the resulting product was named ZIF‐7@PMO. The surface functionalization with the PMO nanoparticles enhanced the chemical stability of ZIF‐7 nanoparticles in ethanol. The study examined the impact of temperature on the synthesis of ZIF‐7@PMO and found that low temperatures were more conducive to the encapsulation of ZIF‐7 nanoparticles and fluorescent organosilica, as well as pore size retention. Moreover, the drug storage capacity of the ZIF‐7@PMO nanoparticles was evaluated via their loading and release of 5‐FU. The results revealed that the ZIF‐7@PMO nanoparticles could adsorb 5‐FU with a loading capacity of 100–140 mg g−1 for 24 h. ZIF‐7@PMO released half of 5‐FU amount within 8 h before releasing a maximum of 75 % within 3 days. Therefore, the fluorescent ZIF‐7@PMO nanoparticles could be a potential drug carrier in the field of controlled drug delivery.

Three-Dimensional Metal-Organic Framework@Cellulose Skeleton-Reinforced Composite Polymer Electrolyte for All-Solid-State Lithium Metal Battery.

High-safety and high-energy-density solid-state lithium metal batteries (SSLMBs) attract tremendous interest in both academia and industry. Especially, composite polymer electrolytes (CPEs) can overcome the limitations of single-component solid-state electrolytes. In this work, a strategy of combining a rigid functional skeleton with a soft polymer electrolyte to prepare reinforced CPEs was adopted. The in situ grown zeolitic imidazolate frameworks (ZIFs) with three-dimensional cellulose fiber skeleton (ZIF-67@CF) and succinonitrile (SN) plasticizer into poly(ethylene oxide) (PEO) together form ZIF-67@CF/PEO-SN CPEs. The addition of ZIF-67@CF and SN to PEO synergistically enhanced the physical and electrochemical properties of CPEs. Furthermore, the conduction mechanism of lithium-ion (Li+) in CPEs was studied using density functional theory. It is impressive that the ZIF-67@CF/PEO-SN CPEs at 30 °C exhibit a high ionic conductivity of 1.17 × 10-4 S cm-1, a competitive Li+ transference number of 0.40, a wide electrochemical window of 5.0 V, a notable tensile strength of 18.7 MPa, and superior lithium plating/stripping stability (>550 h at 0.1 mA cm2). Such favorable features endowed LiFePO4/(ZIF-67@CF/PEO-SN)/Li cell at 30 °C with a high discharging capacity (152.5 mA h g-1 at 0.2 C), a long cycling lifespan (>150 cycles with 99% capacity retention), and superior operating safety. This work provides insights and promotes the application of functionalized CPEs for SSLMBs.

Amino Functionality Enables Aqueous Synthesis of Carboxylic Acid-Based MOFs at Room Temperature by Biomimetic Crystallization.

Enzyme immobilization within metal-organic frameworks (MOFs) is a promising solution to avoid denaturation and thereby utilize the desirable properties of enzymes outside of their native environments. The biomimetic mineralization strategy employs biomacromolecules as nucleation agents to promote the crystallization of MOFs in water at room temperature, thus overcoming pore size limitations presented by traditional postassembly encapsulation. Most biomimetic crystallization studies reported to date have employed zeolitic imidazole frameworks (ZIFs). Herein, we expand the library of MOFs suitable for biomimetic mineralization to include zinc(II) MOFs incorporating functionalized terephthalic acid linkers and study the catalytic performance of the enzyme@MOFs. Amine functionalization of terephthalic acids is shown to accelerate the formation of crystalline MOFs enabling new enzyme@MOFs to be synthesized. The structure and morphology of the enzyme@MOFs were characterized by PXRD, FTIR, and SEM-EDX, and the catalytic potential was evaluated. Increasing the linker length while retaining the amino moiety gave rise to a family of linkers; however, MOFs generated with the 2,2'-aminoterephthalic acid linker displayed the best catalytic performance. Our data also illustrate that the pH of the reaction mixture affects the crystal structure of the MOF and that this structural transformation impacts the catalytic performance of the enzyme@MOF.

Ameliorating carbon capture efficiency of polysulfone membranes via collegial incorporation of zeolite imidazole frameworks and carbon nanotubes

AbstractContinuously exacerbating situation of global warming can be effectively mitigated by controlling carbon emissions from combustion processes through economically attractive membrane technology. Carbon capture efficiency of prospective membranes can be significantly improved via synergistically incorporating CO2‐selective ZIF‐300 nanoparticles and carbon nanotubes (CNTs) into polysulfone (PSF) matrix. Solution‐casting coupled with phase‐inversion processes were employed to concoct hybrid membranes containing varying loadings of both nanofillers. Manufactured composite membranes showed improved matrix structure, uniform nanofillers scattering, enhanced thermal resistance, and ameliorated nanofillers‐polysulfone interfacial adhesion as evidenced by morphological and thermal analysis. Both sorption and permeation measurements for CO2 and N2 gases performed on created membranes indicated upgraded CO2 permeability and CO2/N2 permselectivity on account of collegial impact of added nanofillers. In contrast to pristine polysulfone membrane rendering CO2 intake of 4.1 and CO2/N2 sorption selectivity of 12, hybrid membrane containing 15% ZIF‐300 and 3% CNTs uplifted corresponding values to 12 and 22, respectively. As compared to unadulterated polysulfone membrane, CO2 permeability and CO2/N2 permselectivity of hybrid membrane doped with optimized nanofillers loading of were, respectively, elevated by five‐ and three‐folds. Unique features of manufactured membranes can best be manifested in terms of their ability to maintain gas separation performance from post‐combustion effluents.

Electrodeposited ZIF-67 reinforced polypyrrole coating on ferritic stainless steel substrate with durable anticorrosion performance

The harsh acidic environment containing chloride ions has created serious corrosion hazards for ferritic stainless steels. Zeolitic imidazole frameworks (ZIFs) are a promising material for corrosion protection due to their microstructural and physicochemical properties. In this study, we proposed the electrodeposited ZIF-67 reinforced polypyrrole (PPY) coating (PPY/ZIF-67) for corrosion protection of 430 ferritic stainless steel (430SS). The morphology, microstructure, and anticorrosion behavior of the pristine PPY and hybrid PPY/ZIF-67 coating systems were characterized. The successful electrodeposition of ZIF-67 nanoparticles on the surface of the PPY layer resulted in a uniform distribution and a compact coating structure, which contributed to the overall uniformity of the coating and enhanced both the barrier and activity inhibition functions of the coating. The protective performance of PPY/ZIF-67 coatings was evaluated through electrochemical tests, the results indicated that the anticorrosion efficiency of PPY/ZIF-67 coating (with 0.4 mol/L pyrrole monomer content) reached to 99 %, and the coating demonstrated a durable corrosion protection ability (744 h) in 0.1 mol/L HCl solution. Such performance of can be attributed to the combined effect of the anodic protection provided by the inner PPY film, the active corrosion inhibiting properties of the ZIF-67 nanoparticle layer, and the hindrance of aggressive species by the compact coating structure over the prolonged service time.

Enhanced adsorption and removal of Cd(II) from aqueous solution by amino-functionalized ZIF-8

Zeolite imidazolate framework-8 (ZIF-8), which is a special subgroup of metal–organic frameworks (MOFs), was synthesized and modified by ethylenediamine (ZIF-8-EDA) to prepare an efficient adsorbent for the high sorption of Cd2+ ions from solution. The synthesized and modified ZIF-8 (ZIF-8-EDA) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. The optimum conditions for dosage of adsorbent, initial ion concentration, pH, and contact time were 0.05 g/l, 50 mg/l, 6, and 60 min, respectively, for cadmium ion sorption from aqueous solutions with a removal efficiency of 89.7% for ZIF-8 and 93.5% for ZIF-8-EDA. Adsorption kinetics and equilibrium data were analyzed using the Langmuir and Freundlich equations. The Langmuir model fitted the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for the cadmium ions was 294.11(mg/g). The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was feasible, spontaneous, and endothermic at 20–50 °C. Based on the results, the amino functionalized ZIF-8 had improved adsorption performance due to the replacing of the starting linker with organic ligands that had effective functional groups, leading to chemical coordination due to the interaction of metal ions with the non-bonding pair of electrons on the N atoms of the amino functional group. The selectivity toward metal ion adsorption by ZIF-8-EDA was Cd2+ > Pb2+ > Ni2+‏.

Efficiency of magnetic zeolitic imidazolate framework-8 (ZIF-8) modified graphene oxide for lead adsorption.

Simple and efficient removal of Pb(II) ion from aqueous solution through adsorption has accelerated the development of many new composites to improve this popular method. In this study, the composites of graphene oxide (GO), zeolitic imidazolate framework-8 (ZIF-8), and magnetic materials were synthesized via coprecipitation method utilizing a different molar ratio between FeCl2 and FeCl3 of 1:0.5, 2:1, 3:1.5, and 4:2. The ZIF-8/GO was prepared via room temperature synthesis method prior to its further modification with magnetic materials for ease of separation. It was observed that the MZIF-8/GO2 of molar ratio 2:1 showed the best performance in adsorbing Pb(II) ion. As confirmed by FESEM image, it appeared to be ZIF-8 particles that have grown all over the GO platform and overlayed with Fe3O4 granular-shaped particles. The MZIF-8/GO2 successfully achieved 99% removal of Pb(II) within 10min. The optimum values obtained for the initial concentration of Pb (II) were 100mg/L, pH of 4 to 6, and adsorbent dosage used was 10mg. The Langmuir isotherm and the pseudo-second-order kinetic model were deemed suitable to evaluate the adsorption of Pb(II) using MZIF-8/GO2. Results showed that MZIF-8GO2 achieved a maximum adsorption capacity of 625mg/g of Pb(II) adsorption. All parent materials demonstrated a good synergistic effects, while exhibiting a significant contribution in providing active sites for Pb(II) adsorption. Therefore, this ternary composite of MZIF-8/GO2 is expected to be a promising adsorbent for Pb(II) adsorption from aqueous solution with an added value of ease of post phase separation using external magnetic field.

Synergistic Effect of ZIF-8 and Pt-Functionalized NiO/In2O3 Hollow Nanofibers for Highly Sensitive Detection of Formaldehyde

A rapid and accurate monitoring of hazardous formaldehyde (HCHO) gas is extremely essential for health protection. However, the high-power consumption and humidity interference still hinder the application of HCHO gas sensors. Hence, zeolitic imidazolate framework-8 (ZIF-8)-loaded Pt-NiO/In2O3 hollow nanofibers (ZPNiIn HNFs) were designed via the electrospinning technique followed by hydrothermal treatment, aiming to enable a synergistic advantage of the surface modification and the construction of a p-n heterostructure to improve the sensing performance of the HCHO gas sensor. The ZPNiIn HNF sensor has a response value of 52.8 to 100 ppm HCHO, a nearly 4-fold enhancement over a pristine In2O3 sensor, at a moderately low temperature of 180 °C, along with rapid response/recovery speed (8/17 s) and excellent humidity tolerance. These enhanced sensing properties can be attributed to the Pt catalysts boosting the catalytic activity, the p-n heterojunctions facilitating the chemical reaction, and the appropriate ZIF-8 loading providing a hydrophobic surface. Our research presents an effective sensing material design strategy for inspiring the development of cost-effective sensors for the accurate detection of indoor HCHO hazardous gas.

The role of annealing in optimizing the electrical, linear, and nonlinear optical properties ZIf-8@TiO2 films for possible use in photonic and optoelectronic devices

Abstract Here, we fabricate zeolitic imidazolate framework-8 (ZIF-8)–doped 5 wt. % nanosized TiO2 (ZIf-8@TiO2) thin films using a vapor coating unit. The effects of annealing up to 473 K on the physical characteristics of fabricated ZIf-8@TiO2 thin films were studied. XRD, FTIR, and UV-Vis spectroscopy were utilized to investigate the structural properties of the as-deposited and annealed samples. An increase of approximately 18% was observed in the electrical conductivity. As the annealing temperature increased, the light transmission decreased. This could be due to the growth or aggregation of TiO2 particles during annealing. Raising the annealing temperature by 100 K enhanced the refractive index (n) and energy gap (Eg) by approximately 33% and 8%, respectively. The decrease in ε1 and ε2 in response to the annealing temperature increase was due to the evaporation of MOF organic linkers. The nonlinear optical results indicated a dependence on the annealing temperatures that improved charge carrier mobility and coherent light-matter interactions. Our thesis findings can improve the overall performance and efficiency of optoelectronic devices.

Zeolitic Imidazolate Frameworks Based Anticancer Drug Delivery System Associated with Dual Action of Surface Charge and Lewis Base Ligand

AbstractZeolitic imidazole frameworks (ZIFs), which combine the favorable characteristics of tunable porosity, controlled structure, and facile functionalization, are explored as a novel class of nanocarriers for biomedical applications. In this study, different ZIF materials are investigated, including ZIF‐8, ZIF‐67, ZIF‐90, ZIF‐92, and ZIF‐108, with the same sodalite topology as the adenosine‐5′‐triphosphate (ATP)‐triggered drug delivery systems. Results indicated that ZIF‐90 and ZIF‐108 displayed good biological compatibility and efficiently accumulated in the mitochondria through competitive coordination between the metal nodes of the ZIFs and ATP, suggesting efficient intracellular delivery. With further interactions between these metal ions and ATP, the encapsulated drugs are released from the ZIF nanoparticles, thereby achieving optimal anti‐tumor activity. Through a systematic evaluation of the physicochemical properties of different ZIFs, it demonstrates that the surface charges of ZIFs have a significant impact on the cytotoxicity of cells, whereas the Lewis basicity of imidazole‐based ligands plays an essential role in the competitive coordination between the metal ions and ATP. These findings provide a potential method for screening ZIFs based nanocarriers with minimal toxicity and explain the different delivery efficiencies of these materials with similar topologies.

Conjugating HA bundles with ZIF-8 for catalytic degradation of tetracycline and antibacterial capacity

The overused of antibiotics had led to major environmental issues and drug-resistant bacteria, which inevitably harmed the environment and public health. In this work, in order to obtain environmentally friendly bi-functional materials to combat with residual antibiotics and bacterial contamination, ZIF-8, a typical Zn based zeolitic imidazolate framework (ZnZIF) with excellent chemical stability, was conjugated to hydroxyapatite nanowire bundles (HAnBs) by a simple in-situ synthesis. The obtained ZnZIFs@HAnBs was characterized by SEM, EDS, XPS, FT-IR, XRD and BET. The effects of catalysts, catalyst dosage, TC initial concentration, PMS concentration and pH on TC degradation were investigated. Notably, ZnZIFs@HAnBs (94.0 %) exhibited excellent degradation effect of tetracycline (TC) within 15 min, which was 1.7 and 5.2 times than that of ZIF-8 (55.9 %) and HAnBs (18.1 %) under optimal conditions, respectively. Moreover, after recycling 10 times, the degradation rate still more than 86.8 %. The degradation mechanism was confirmed by free radical quenching experiment coupling with electron paramagnetic resonance (EPR), and the 1O2 and O2•- were the major reactive oxygen species in TC degradation. Furthermore, it presented excellent antibacterial activity (95.0 %) against E. coli and S. aureus, which was attributed to the synergistic effect of sustained release of Zn2+ and phosphate in ZnZIF@HAnBs. In summary, an eco-friendly bi-functional materials of HA nanowire bundles could be synthesized by simple strategy, and it could be applied in the fields of environmental remediation, as well as in treatment of antibiotic and bacterial pollution.

The Optimal Doping Ratio of Fe2O3 for Enhancing the Electrochemical Stability of Zeolitic Imidazolate Framework-8 for Energy Storage Devices

This paper aims to discover a novel composite material that has great potential for manufacturing high-performance supercapacitors suitable for diverse applications, such as electric vehicles, portable electronics, and stationary energy storage systems. Zeolitic imidazolate framework-8 (ZIF-8) doped by different concentrations up to 5 wt.% of nanosized Fe2O3 have been prepared (ZIF-8/Fe2O3). The effect of doping ratio 1, 3, and 5 wt.% on the structural and electrochemical properties of ZIF-8/Fe2O3 has been investigated. The structural characterization has been carried out using TGA, BET, XRD, and FTIR. The XRD analysis revealed that the crystalline size of our sample increased by approximately 16% as a result of doping ZIF-8 with 5 wt.% of Fe2O3. The structural analysis of the doped samples revealed that the material exhibited enhanced thermal stability and porosity, with an increase of approximately 105 m2/g. The introduction of doped nanometal oxides improved the capacitance value of ZIF-8 by significantly increasing its surface area. Additionally, the electron transport efficiency within ZIF-8/5 wt.% Fe2O3/electrode is increased. The Nyquist plot decreases as the doping of Fe2O3 increases. This indicates a decrease in the charge transfer resistance at the electrode–electrolyte interface, which is desired in applications such as batteries, fuel cells, or electrochemical sensors where faster electron transfer is needed for improved performance.

Nonenzymatic dual glucose sensing on boronic acid modified zeolitic imidazolate framework-67 nanoparticles for diabetes management.

For early diabetes identification and management, the progression of an uncomplicated and exceedingly responsive glucose testing technology is crucial. In this study, we present a new sensor incorporating a composite of metal organic framework (MOF) based on cobalt, coated with boronic acid to facilitate selective glucose binding. Additionally, we successfully employed a highly sensitive electro-optical immunosensor for the detection of subtle changes in concentration of the diabetes biomarker glycated haemoglobin (HbA1c), using zeolitic imidazolate framework-67 (ZIF-67) coated with polydopamine which further modified with boronic acid. Utilizing the polymerization characteristics of dopamine and the NH2 groups, a bonding structure is formed between ZIF-67 and 4-carboxyphenylboronic acid. ZIF-67 composite served as an effective substrate for immobilising 4-carboxyphenylboronic acid binding agent, ensuring precise and highly selective glucose identification. The sensing response was evaluated through both electrochemical and optical methods, confirming its efficacy. Under optimized experimental condition, the ZIF-67 based sensor demonstrated a broad detection range of 50-500mg dL-1, a low limit of detection (LOD) of 9.87mg dL-1 and a high correlation coefficient of 0.98. Furthermore, the 4-carboxyphenylboronic acid-conjugated ZIF-67-based sensor platform exhibited remarkable sensitivity and selectivity in optical-based detection for glycated haemoglobin within the clinical range of 4.7-11.3%, achieving a LOD of 3.7%. These findings highlight the potential of the 4-carboxyphenylboronic acid-conjugated ZIF-67-based electro-optical sensor as a highly sensitive platform for diabetes detection.

One-pot synthesis of a porphyrin functionalized metal-organic frameworks as a recyclable visible-light-driven photosensitizer for efficient detoxification of a sulfur mustard simulant in air

Herein, we report a facile one-pot in situ self-assembly approach that enables a porphyrin photosensitizer, [5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin]-Zn(II) (ZnTPP), to be enshrouded by a zeolitic imidazolate framework-8 (ZIF-8) to afford a novel visible-light-driven heterogeneous photosensitizer, ZnTPP@ZIF-8 composite. The ZnTTP photosensitizer was well dispersed and fully confined within the ZIF-8 crystals and the framework intactness and porosity were well maintained. The as-prepared ZnTPP@ZIF-8 composite integrates the advantages of ZIF-8 MOFs and ZnTTP photosensitizer. It not only can effectively produce both singlet oxygen (1O2) and superoxide ion (∙O2−) under visible light irradiation, but also exhibit high surface area and excellent stability. The structure characterization of ZnTPP@ZIF-8 composite was first carried out, and then this material can be used as a heterogeneous photosensitizer for the rapid and highly selective detoxification of a sulfur mustard simulant (2-chloroethyl ethyl sulfide) into the corresponding much less toxic sulfoxide product with a half-life of only 1.5 min under visible light irradiation at room temperature in air atmosphere. This catalyst can be readily recycled and reused at least six times without obvious loss of catalytic activity. This study will provide us a new strategy for the facile, rapid and environmentally friendly preparation of photosensitizer@MOFs composites and the rapid detoxification of sulfur mustard under ambient conditions in the future.

Trypsin Encapsulation in the Zeolitic Imidazolate Framework for Low-Molecular Weight Protein Analysis with High Selectivity and Efficiency.

Low-molecular weight proteins (LWPs) are important sources of biological information in biomarkers, signaling molecules, and pathology. However, the separation and analysis of LWPs in complex biological samples are challenging, mainly due to their low abundance and the complex sample pretreatment procedure. Herein, trypsin modified by poly(acrylic acid) (PAA) was encapsulated by a zeolitic imidazolate framework (ZIF-L). Mesopores were formed on the ZIF-L with the introduction of PAA. An alternative strategy for separation and pretreatment of LWPs was developed based on the prepared ZIF-L-encapsulated trypsin with adjustable pore size. The mesoporous structure of the prepared materials selectively excluded high-molecular weight proteins from the reaction system, allowing LWPs to enter the pores and react with the internal trypsin, resulting in an improved separation efficiency. The hydrophobicity of the ZIF-L simplified the digestion process by inducing significant structural changes in substrate proteins. In addition, the enzymatic activity was significantly enhanced by the developed encapsulation method that maintained the enzyme conformation, allowed low mass transfer resistance, and possessed a high enzyme-to-substrate ratio. As a result, the ZIF-L-encapsulated trypsin can achieve highly selective separation, valid denaturation, and efficient digestion of LWPs in a short time by simply mixing with substrate proteins, greatly simplifying the separation and pretreatment process of the traditional hydrolysis method. The prepared materials and the developed strategy demonstrated an excellent size-selective assay performance in model protein mixtures, showing great potential in the application of proteomics analysis.

Microfluidic chemistry assisted synthesis of cobalt quantum dot embedded nitrogen doped carbon with oxidase-like properties toward ascorbic acid detection

Ascorbic acid (AA) is a powerful antioxidant in food safety and disease treatment. It is of great significance to develop a low-cost, high-stability, and easy-to-operate colorimetric method for quantitative detection of AA in food or human body. Although various nanozymes have been developed for the colorimetric detection of AA, the size regulation of the catalytic center of nanozymes remains a challenge. In this work, we propose a combined strategy of flow chemistry synthesis and pyrolysis to realize the controllable adjustment of the catalytic center size of nanozymes. Zinc-cobalt zeolitic imidazole frameworks (ZnCo-ZIFs) with different sizes are synthesized by flow chemistry. Nitrogen-doped carbon materials with different Co catalytic centers (80 nm–10 nm) are then obtained by pyrolysis of ZnCo-ZIFs precursors. Among them, cobalt quantum dot embedded nitrogen-doped carbon (Co QDs/N-C) exhibits excellent oxidase activity, with Vmax and Km of 4.19 × 10−7 M s−1 and 0.12 mM. Therefore, a simple, low-cost, and stable colorimetric method for the detection of AA is established with a good linear relationship (3–500 μM) and low detection limit (0.40 μM). This work has certain guiding significance for the size regulation of catalytic center of nanozyme, and the detection method has broad application prospects in biochemical sensing field.

Synergistic expression of ZIF-67 and amphiphilic polymer hydrogel in multi-mode liquid chromatographic separation

In this work, zeolitic imidazolate framework-67 (ZIF-67) with excellent stability synthesized at room temperature was used together with amphiphilic polymer hydrogel to synthesize a captivating mixed-mode silica stationary phase for the first time. The amphiphilic polymer hydrogel prepared by weakly basic cationic and acidic anionic monomers that was modified on the surface of ZIF-67@SiO2 by a simple physical coating method not only improved the separation performance, but also enhanced the applicability of ZIF-67@SiO2 in chromatographic analysis. Meanwhile, the porous ZIF-67 effectively alleviated the problem that polymer hydrogel was easy to swell. To sum up, the amphiphilic polymer hydrogel and ZIF-67 showed excellent synergistic effect in improving the separation ability and the applicability of stationary phase. The experimental results demonstrated that the ZIF-67/hydrogel@SiO2 stationary phase could be applied in various chromatographic separation modes, demonstrating superior resolution and separation selectivity for polycyclic aromatic hydrocarbons, steroid hormones, nucleosides, B-vitamins, sulfonamides, benzoic acids and dinitrobenzene isomers. In this study, the synergistic expression of ZIF-67 and polymer hydrogel provided a new idea for the development of silica stationary phase co-modified by metal-organic framework and hydrogel material. Concurrently, the successful preparation of ZIF-67/hydrogel@SiO2 composite revealed a new possibility for utilizing ZIF-67 as the functional material of stationary phase, expanding the application potential of ZIF-67 in the field of chromatography.

Effect of Boron-Doping on Gate-Opening CO2 Adsorption in Zinc-Benzimidazolate Coordination Networks.

Flexible metal-organic frameworks (MOFs) have attracted much attention as selective gas adsorption and storage. This report describes boron doping in zeolitic imidazolate framework-7 (B-ZIF-7), which exhibits reversible phase transition during CO2 adsorption/desorption. We have successfully prepared B-ZIF-7 coordination networks using boron-bridged benzimidazolate (B(bim)4-) as organic ligands. Powder X-ray diffraction (PXRD) measurements and infrared spectroscopy revealed that B-ZIF-7 has a crystal structure similar to that of ZIF-7 while containing boron bridging in the coordination network. Since B-ZIF-7 forms a cationic coordination network, the guest anions are encapsulated within the pore. CO2 adsorption/desorption measurements at 300 K showed that B-ZIF-7(NO3), which contains nitrate ions (NO3-) as guest anions in its pores, exhibits a S-shaped CO2 adsorption/desorption isotherm, which is characteristic of gate-opening type MOFs. Compared with ZIF-7, B-ZIF-7(NO3) has superior CO2 adsorption capacity in the low-pressure and superior CO2 storage capacity. The CO2 adsorption and desorption behavior of B-ZIF-7(NO3) was analyzed by in situ temperature-controlled PXRD measurements and thermogravimetric analysis under a CO2 atmosphere, and a reversible phase transition was observed. We have also successfully prepared B-ZIF-7(Cl) and B-ZIF-7(OTf) (OTf = CF3SO3-) with different guest anions. The CO2 adsorption/desorption behaviors of B-ZIF-7(Cl) and B-ZIF-7(OTf) were significantly different from those of B-ZIF-7(NO3) and ZIF-7. B-ZIF-7(Cl) showed gate opening at a higher pressure than ZIF-7, and B-ZIF-7(OTf) did not show S-shaped CO2 adsorption isotherm and showed adsorption behavior in micropores. These results indicate that the CO2 adsorption behavior of B-ZIF-7 depends on the interaction between the guest anions and CO2 molecules or the cationic framework and the bulkiness of the guest anions. Boron doping in a coordination network with boron-bridged imidazolate ligands is a promising strategy to increase the gas adsorption capability of porous materials.

Facile functionalization iron in zeolitic imidazole framework-67 under solvent-free conditions for enhancing CO2 fixation reaction

The heterometal functionalization on zeolitic-imidazole frameworks (ZIFs) is a strategy to modify properties over the homometal ZIFs. A green strategy for simultaneously functionalized iron atoms during the crystal formation of ZIF-67 (Fe@ZIF-67) through the solid-solid thermal (SST) method is newly developed. The single-step process and absent solvent conditions are beneficial advantages of this SST method over the early reported synthetic methods. The results show that the iron is well-dispersed and homogeneously coordinated in the structure of Fe@ZIF-67. Moreover, the optimal iron-functionalized ZIF-67 (20Fe@ZIF-67) significantly enhances the catalytic performance of CO2 cycloaddition epoxide by 2.3 times compared to pristine ZIF-67 under mild reaction conditions. The DFT calculation reveals that the iron atom induces the unsaturated sites or defect structure on the Fe@ZIF-67 catalyst, providing more reactive sites for the catalytic activity of the reaction.