Imidazolate Framework Research Articles

Insight into the molecular mechanism of organic pollutants’ adsorption on magnetic ZIF-8 synthesized via a transformational route

This study presents the synthesis of Fe3O4@Zeolite Imidazolate Framework-8 (Fe3O4@ZIF-8), a novel magnetic core–shell adsorbent engineered for enhance adsorption of organic pollutants. The process begins with the formation of spherical magnetite aggregates (i.e., Fe3O4) via a solvothermal method, using polyacrylic acid for stabilization and capping. A ZIF-8 shell is then grown through a sol gel process followed by reaction with 2-methylimidazole, resulting in a crystalline shell approximately 60 nm thick. Characterization techniques, including energy dispersive X-ray analysis and X-ray diffraction, confirm the successful preparation of Fe3O4@ZIF-8. The adsorption capabilities were evaluated using methylene blue (MB) and diclofenac sodium (DCF) as model pollutants. Fe3O4@ZIF-8 demonstrated rapid removal efficiencies, with 98 % removal of MB (6.01 × 10-4 mg·g−1·min−1) and DCF (4.43 × 10-4 g·mg−1.min−1) within 15 and 30 min, respectively, significantly outperforming conventional activated carbon. Thermodynamic studies indicate that the adsorption processes are spontaneous; enthalpic changes drive MB adsorption, while DCF is influenced by entropic factors. Molecular modeling reveals preferential adsorption behaviors on different ZIF-8 facets, with stronger interactions for MB due to π-π stacking and hydrogen bonding. These findings underscore the potential of Fe3O4@ZIF-8 as an effective adsorbent for water purification, highlighting its substantial adsorption capacity (73.2 mg·g−1 for MB and 53.8 mg·g−1 for DCF), stability, and reusability.

Novel and simple electrochemical sensing platform based on polypyrrole nanotubes/ZIF-67 nanocomposite/screen printed graphite electrode for sensitive determination of metronidazole

Here, a simple, fast, and sensitive voltammetric sensor based on screen printed graphite electrode (SPGE) modified with polypyrrole nanotubes/zeolitic imidazolate framework-67 (PPy NTs/ZIF-67) nanocomposite is introduced for the metronidazole (MNZ) determination. The PPy NTs/ZIF-67 nanocomposite was synthesized and characterized by using X-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The developed sensor based on PPy NTs-ZIF-67 nanocomposite modified SPGE shows an obvious reduction peak at −650 mV for MNZ, mainly due to the synergistic effects of the ZIF-67 and PPy NTs. Differential pulse voltammetry (DPV) was found to be the most suitable method for MNZ detection, showing a linear dynamic range of 0.01 to 500.0 µM and a low limit of detection (LOD) of 0.004 µM. In investigating the practicability, the PPy NTs/ZIF-67/SPGE sensor demonstrated efficient practicability with satisfactory recoveries (97.1 % to 103.5 %) and low relative standard deviation (RSD) values of 1.8–3.6 % for MNZ determination in MNZ tablets and urine samples.

Integrating self-hygroscopic hydrogel electrolyte and porous electrode for supercapacitor operating in variable humidity environments

The application of supercapacitors (SCs) based on the conventional polyvinyl alcohol‑potassium hydroxide (PVA-KOH) polymer electrolyte is challenged in variable humidity environments, especially in low relative humidity (RH) environments. Herein, taking advantage of the high ionic conductivity and strong hygroscopicity of highly concentrated KOH solutions, we have prepared a hygroscopic hydrogel polymer electrolyte composed of sodium alginate (SA)/PVA/poly(acrylic acid) (PAA)-KOH. The SA/PVA/PAA-KOH gel electrolyte exhibits high ionic conductivity, superior water retention and even water adsorption capability. A three-dimensional CoCu-layered double hydroxide/zeolitic imidazole framework-67 (CuCo-LDH/ZIF-67) porous electrode has also been prepared for the construction of the high-performance SC operating in variable RH environments. The CuCo-LDH/ZIF-67 porous electrode allows deep penetration of the self-hygroscopic electrolyte, facilitating electron/ion diffusion and providing fast water transport channels. As a result, our asymmetric SC show significantly improved electrochemical performance than that of SC based on conventional PVA-KOH electrolyte under different RH environments. This integration strategy can advance the practical application of SC in extreme environments.

Revolutionizing protein hydrolysis in wastewater: Innovative immobilization of metagenome-derived protease in periodic mesoporous organosilica with imidazolium framework

This research focused on utilizing periodic mesoporous organosilica with imidazolium framework (PMO-IL), to immobilize a metagenome-sourced protease (PersiProtease1), thereby enhancing its functional efficiency and catalytic effectiveness in processing primary proteins found in tannery wastewater. The successful immobilization of enzyme was confirmed through the use of N2 adsorption-desorption experiment, XRD, FTIR, TEM, FESEM, EDS and elemental analytical techniques. The immobilized enzyme exhibited greater stability in the presence of various metal ions and inhibitors compared to its free form. Furthermore, enzyme binding to PMO-IL nanoparticles (NPs) reduced leaching, evidenced by only 11.41 % of enzyme leakage following a 120-min incubation at 80 °C and 6.99 % after 240 min at 25 °C. Additionally, PersiPro@PMO-IL maintained impressive operational consistency, preserving 62.24 % of its activity over 20 cycles. It also demonstrated notable stability under saline conditions, with an increase of 1.5 times compared to the free enzyme in the presence of 5 M NaCl. The rate of collagen hydrolysis by the immobilized protease was 46.82 % after a 15-minute incubation at 60 °C and marginally decreased to 39.02 % after 20 cycles indicative of sustained efficacy without significant leaching throughout the cycles. These findings underscore the effectiveness of PMO-IL NPs as a viable candidate for treating wastewater containing protein.

Sensitive determination of the cardiac drug isoproterenol in the presence of acetaminophen using modified electrode with multiwall carbon nanotube/ZnCo-Zeolite imidazole frameworks and ionic liquid

Isoproterenol (ISO) is a synthetic amine that used to treat heart attacks, allergic emergencies, bronchitis, and cardiac chock. But on the other hand, excessive use of ISO can cause a significant decrease in blood pressure, as well as cause heart failure and/or cardiac arrhythmia, or in sometimes cause vasodilation of skeletal muscle arteries. Therefore, determination of ISO in various specimens is very important. The present attempt was made to introduce a sensitive electrochemical sensor by using carbon paste electrode (CPE) modified with multiwall carbon nanotubes/ZnCo-Zeolite imidazole frameworks and ionic liquid for determination of ISO at the presence of acetaminophen (AC). The characteristics of the as-fabricated sensor were explored via scanning electron microscope, Fourier transfer infra-red spectroscopy and X-ray powder diffraction. The electro-oxidation current of ISO onto the modified electrode surface was linear in the range of 0.04–580.0 μM and a limit of detection 9.8 nM was calculated according to 3Sb/m. For assesses the practical applicability of the modified electrode, the values of ISO and AC in serum and urine samples were determined using the calibration plot and as a result, appropriate relative standard deviations (2.6–3.5 %) and recoveries (97.2–103.9 %) were obtained.

Constructing bio-inspired anion channels by dual-ligand MOF in membranes for efficient CO2 separation

One of the biggest challenges of Pebax-based membranes is how to simultaneously achieve high CO2 permeability and selectivity. Hence, three-dimensional L-histidine@zeolitic imidazole framework-8 (His@ZIF-8 (X)) was synthesized as dual-ligand metal-organic framework (MOF), and it was incorporated into the Pebax 1657 matrix to fabricate mixed matrix membranes (MMMs) for efficient CO2 separation. The three-dimensional His@ZIF-8 (X) with abundant His mimicked anion transport protein, and it constructed bio-inspired anion transport channels. His@ZIF-8 (X) played important functions when it was incorporated into the MMMs: the bio-inspired active sites of His@ZIF-8 with the Zn2+ bonded to three Hmim and one water molecule had similar function with the active sites in carbonic anhydrase (CA), which can catalyze CO2 into water-soluble bicarbonate (HCO3−). Subsequently, the bio-inspired anion transport channels allowed HCO3− to rapidly transport, because they had His residues that can form anion-dipole interactions with HCO3− in His@ZIF-8 (X). Therefore, Pebax 1657/His@ZIF-8 (X) MMMs were endowed with the excellent separation performance due to the bio-inspired anion transport channels constructed by His@ZIF-8 (X). In particularly, MMM contained 4 wt% His@ZIF-8 (12.5) achieved the optimal separation performance with a CO2 permeability of 541 ± 9 Barrer and CO2/CH4 selectivity of 35 ± 0.6. The work implies that the construction of the bio-inspired anion transport channels within MMMs was a potential strategy for efficient CO2 separation.

Rapid Synthesis and Microenvironment Optimization of Hierarchical Porous Fe─N─C Catalysts for Enhanced ORR in Microbial Fuel Cells.

Here, an approach to produce a hierarchical porous Fe-N-C@TABOH catalyst with densely accessible high intrinsic active FeNx sites is proposed. The method involves a single-step pyrolysis of Zn/Fe-zeolitic imidazolate framework (Zn/Fe-ZIF-H) with tetrabutylammonium hydroxide (TABOH) micelles, which is obtained by utilizing TABOH as a structural template and electronic mediator at room temperature for a brief duration of 16min. Notably, the yield of Zn/Fe-ZIF-H is 3.5 times that of Zn/Fe-ZIF-N prepared by conventional method. Results indicate that in addition to expediting synthesis and increasing yield of the Zn/Fe-ZIF-H, the TABOH induces a hierarchical porous structure and fosters the formation of more and higher intrinsic active FeNx moieties in Fex-N-C@TABOH, showing that TABOH is a multifunctional template. Crucially, the increased mesoporosity/external surface area and optimized microenvironment of Fe-N-C@TABOH significantly enhance ORR activity by facilitating the formation of high intrinsic active FeNx sites, increasing accessible FeNx sites, and reducing mass transfer resistance. Through structure tailoring and microenvironment optimization, the resulting Fe-N-C@TABOH exhibits superior ORR performance. DFT calculation further validates that the synergistic effect of these two factors leads to low ORR barrier and optimized *OH adsorption energy. This study underscores the importance of structure and electronic engineering in the development of highly active ORR catalysts.

Single atoms/metal nanoparticles-decorated hollow carbon spheres as oxygen reduction catalyst for zinc-air batteries

Non-platinum electrocatalyst development for improving the oxygen reduction reaction (ORR) is critical in electrochemical energy conversion applications such as zinc-air batteries (ZABs). Herein, we developed dual Fe-Co single atoms and Co nanoparticles embedded N-doped hollow carbon (Fe-Co/N-HCS-x) catalysts via the carbonization of polypyrrole (PPy)@zeolitic imidazolate framework (ZIF) core–shell particles, with various PPy concentrations. PPy serves as a secondary nitrogen source that enhances nitrogen amount and promotes metal dispersion to increase active sites density. The Fe-Co/N-HCS-x catalysts with optimized PPy concentration control demonstrated improved ORR performance in alkaline media, with a half-wave potential (E1/2) of 0.921 V and an onset potential (Eonset) of 1.019 V. Fe-Co/N-HCS-x also exhibited high ZABs performance, with a power density of 244.6 mW cm−2 and an operating time of more than 100 h. Our research contributes to the development of optimized active sites for ORR, which can be applied to new electrochemical storage and conversion systems.

Zeolitic imidazolate framework derived Fe catalyst electrocatalytic-driven atomic hydrogen for efficient reduction of nitrate to N2

Excessive discharge of nitrogen-containing chemical products into the natural water environment leads to the serious environmental problem of nitrate-nitrogen pollution, threatening the ecological balance and human health. In this study, we propose an efficient denitrification electrochemical method utilizing iron-doped zeolite imidazolium framework derived defective nitrogen-doped carbon (d-FeNC) catalysts. The d-FeNC catalyst exhibited 97 % nitrate removal efficiency and 94 % total nitrogen (TN) removal, and the reaction rate constant was increased from 0.73 h−1 of the Fe-undoped electrocatalyst (d-NC) to 1.11 h−1. The successful synthesis of d-FeNC with carbon defect sites and encapsulated Fe was confirmed by in-depth characterization. In situ electron paramagnetic resonance (EPR) analysis in conjunction with cyclic voltammetry (CV) tests confirmed the carbon substrates with defect enhanced the trapping of atomic hydrogen (H*) on the catalyst surface. Density functional theory (DFT) calculations clarified the doping of Fe facilitated the adsorption of nitrate, resulting in contact of H* with nitrate on the catalyst surface. In the synergy of the defective state organic framework and metal Fe, H* and nitrate realized a collision process. The electrochemical denitrification system achieved an excellent nitrate removal capacity of 7587 mgN·g−1cat in high-concentration nitrate solution and showed excellent stability under various conditions. Overall, this study underscores the potential of defective iron-doped carbon catalysts for efficient electrocatalytic denitrification, providing a promising approach for sustainable wastewater treatment.

Effective enrichment and separation of three flavonoids from Ohwia caudata (Thunberg) H. Ohashi using magnetic layered double hydroxide/ZIF-8 composites and pCEC

In this study, Fe3O4@ZnCr–layered double hydroxide/zeolitic imidazolate frameworks-8 (MLDH/ZIF-8) magnetically functionalized composites were synthesized by co-precipitation and in situ growth based on the advantages of LDHs and ZIF-8 using Fe3O4 nanoparticles as a magnetic substrate to obtain adsorbents with excellent performance. Moreover, the composite was used for the efficient enrichment of flavonoids in Chinese herbal medicines. The internal structures and surface properties were characterized by SEM, Fourier transform infrared spectroscopy, X-ray diffraction and so on. MLDH/ZIF-8 exhibited a large specific surface area and good paramagnetic properties. The MLDH/ZIF-8 magnetic composite was used as a magnetic solid-phase extraction (MSPE) adsorbent, and a MLDH/ZIF-8 MSPE–pressurized capillary electrochromatography coupling method was developed for the separation and detection of flavonoids (luteolin, kaempferol and apigenin) in a sample of the Chinese herb Ohwia caudata (Thunberg) H. Ohashi. The relevant parameters affecting the extraction efficiency were optimized to determine the ideal conditions for MSPE. 5 mg of adsorbent in sample solution at pH 6, vortex extraction for 5 min, elution with 1.5 mL of ethyl acetate for 15 min. The method showed good linearity in the concentration range of 3–50 μg mL−1 with correlation coefficients of 0.9934–0.9981, and displayed a relatively LODs of 0.07–0.09 μg mL−1. The spiked recoveries of all analytes ranged from 84.5% to 122.0% with RSDs (n=3) between 4.5% and 7.7%. This method is straightforward and efficient, with promising potential in the separation and analysis of active ingredients in various Chinese herbal medicines.

Eco-friendly epoxidized Eucommia ulmoides gum based composite coating with enhanced super-hydrophobicity and corrosion resistance properties

Developing a green, non-toxic, and sustainable bio-based anticorrosive coating is significant for achieving the objective of "carbon reduction". In this study, superhydrophobic multilayer coatings based on epoxidized Eucommia ulmoides gum were prepared via a layer-by-layer assembly bottom-up approach, providing comprehensive protection for mild steel. The foundational layer, comprising the epoxidized Eucommia ulmoides gum/industrial lignin composite (EEUG-EHL), exhibited commendable adhesion, impermeability, and corrosion resistance. The intermediate layer was composed of 8-hydroxyquinoline/zeolitic imidazolate framework-8 (8HQ@ZIF-8) nanoparticles, which controlled the release of 8HQ through pH responsiveness and had self-healing properties. Employing a spraying method, a top layer with micro-nanostructured consisting of a modified ZIF-8 nanoparticle was created, inspired by the micro-nano structure observed in cicada wings. The multilayer coating exhibited remarkable super-hydrophobicity (contact angle > 150°, sliding angle < 5°), chemical stability, self-cleaning properties, and anti-fouling properties. Notably, the multilayer coating demonstrated exceptional corrosion resistance, maintaining an impedance modulus of 108 ohm cm2 (at 0.01 Hz) after immersion in a 3.5 wt% NaCl solution for 45 days. This work introduces a novel approach to enhance the corrosion protection of metal equipment, aligning with the "green development" strategy and holding significance in advancing marine anti-corrosion construction.

A dual-signal ratiometric electrochemical aptasensor based on Thi/Au/ZIF-8 and catalytic hairpin assembly for ultra-sensitive detection of aflatoxin B1.

Adual-signal ratiometric electrochemical aptasensor has been developed for AFB1 detection using thionine/Au/zeolitic imidazolate framework-8 (Thi/Au/ZIF-8) nanomaterials and catalytic hairpin assembly (CHA) reaction. Thi/Au/ZIF-8 combined with DNA hairpin 2 (H2) was used as a signal probe. [Fe(CN)6]3-/4- was served as another signal probe, and the IThi/Au/ZIF-8/I[Fe(CN)6]3-/4- ratio was for the first timeutilized to quantify AFB1. AFB1-induced CHA was used to expand the ratio of electrical signals. In the presence of AFB1, H2/Thi/Au/ZIF-8 bound to the electrode via CHA, enhanced the current signal of Thi/Au/ZIF-8. H2 contained the DNA phosphate backbone hindered [Fe(CN)6]3-/4- redox reaction and resulted in a lower [Fe(CN)6]3-/4- current signal. This aptasensor exhibited high specificity for AFB1, a linear range of 0.1pgmL-1 to 100ngmL-1, and a detection limit of 0.089pgmL-1. It demonstrated favorable sensitivity, selectivity, stability, and repeatability. The aptasensor was suitable for detecting AFB1 in peanuts and black tea and holds potential for real sample applications.

Preparation of Ni, Co doped hollow carbon nanocage from core-shell structure ZIF-8@ZIF-67 for nitrobenzene monitoring

Herein, we employed a Ni, Co duplex metal-doped hollow carbon nanocage derived from the core-shell Zeolite imidazole framework-8 (Zn)@Zeolite imidazole framework-67 (Co) (ZIF-8@ZIF-67) for the sensitive electrochemical detection of nitrobenzene (NB). The precursor was created by coating ZIF-67 on the surface of ZIF-8 through the epitaxial growth method, followed by Ni doping. Subsequent pyrolysis resulted in the formation of a Ni, Co duplex metal-doped hollow carbon nanocage. Characterization of the nanocomposite confirmed the unique hollow and porous structure of NiCo/C, maintaining a dodecahedral morphology with a uniform distribution of carbon and transition metal nanoparticles. The NiCo/C-modified electrode exhibits a wide linear dynamic range (0.05–11.22 μM and 11.22–230.06 μM), a lower limit of detection (0.14 μM), superior stability and selectivity for the detection of NB. Moreover, it shows appropriate practicality toward detecting NB in natural water samples.

Electrochemical sensing platform for detection of heavy metal ions without electrochemical signal.

Heavy metal pollution has attracted global attention because of its high toxicity, non-biodegradability, and carcinogenicity. Electrochemical sensors are extensively employed for the detection of low concentrations of heavy metal ions (HMIs). However, their applicability is often limited to the detection of ions that exhibit electrochemical signals exclusively in aqueous solutions. In this study, we proposed a multi-responsive detection platform based on the modification of horseradish peroxidase@zeolitic imidazolate frameworks-8/thionine/gold/ionic liquid-reduced graphene oxide (HRP@ZIF-8/THI/Au/IL-rGO). This platform demonstrated its capability to detect various metal ions, including those without conventional electrochemical signals. The Au/IL-rGO composite structure enhanced the specific surface area available for the reaction. Furthermore, the in situ growth of HRP@ZIF-8 not only shielded the THI signal prior to detection but also protected the electrode material. It was important to note that the introduced edetate disodium dihydrate (EDTA) had the ability to complex with various HMIs. When excess EDTA was present, it could cleave ZIF-8 and release HRP. In the presence of hydrogen peroxide (H2O2), HRP promoted the oxidation of THI previously reduced by the electrode and thus showed excellent sensitivity for HMIs detection. The proposed method overcame the limitation of traditional electrochemical sensors, which solely relied on electrochemical signals for detecting metal ions. This offers a novel approach to enhance electrochemical ion sensing detection.

An in situ one-step route for the synthesis of Fe3O4@ZIF-8 core-shells with a high-peroxidase-like performance for the colorimetric detection of methyl parathion

Methyl parathion (MP) is a broad-spectrum agricultural insecticide. Human exposure to MP can affect the nervous, cardiovascular, and hepatic systems. In this research, a core–shell Fe3O4@zeolitic imidazolate framework-8 (ZIF-8) is developed as a peroxidase mimic for the rapid and simple colorimetric detection of MP. Fe3O4 nanoparticles were wrapped with ZIF-8 by a hydrothermal method to obtain core–shell structural Fe3O4@ZIF-8 nanocomposites. The synthesized Fe3O4@ZIF-8 possessed mimetic properties and effectively catalyzed the conversion of transparent solution to blue upon the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) by H2O2. Further, based on a classical reaction through acetylthiocholine chloride (ATCl) and cholesterol oxidase (ChOx), acetylcholinesterase (AChE) can generate H2O2, and that MP can exert an inhibitory effect on AChE. Within the range of 10 to 200 µg/L, the MP concentration demonstrated a remarkable linear response with the absorbance under optimum conditions, with a detection limit of 6.3 μg/L. Finally, the proposed approach enabled the detection of MP in cabbage. As an artificial peroxidase, Fe3O4@ZIF-8 demonstrated greater affinity for the substrate than horseradish peroxidase, which has a great application prospects in food safety and environmental safety.

Novel pH-responsive alginate-stabilized curcumin–selenium–ZIF-8 nanocomposites for synergistic breast cancer therapy

In this study, a novel selenium@zeolitic imidazolate framework core/shell nanocomposite stabilised with alginate was used to improve the anti-tumour activity of curcumin. The developed alginate-stabilised curcumin-loaded selenium@zeolitic imidazolate framework (Alg@Cur@Se@ZIF-8) had a mean diameter of 159.6 nm and polydispersity index < 0.25. The release of curcumin from the nanocarrier at pH 5.4 was 2.69 folds as high as at pH 7.4. The bare nanoparticles showed haemolytic activity of about 12.16% at a concentration of 500 µg/mL while covering their surface with alginate reduced this value to 5.2%. By investigating cell viability, it was found that Alg@Cur@Se@ZIF-8 caused more cell death than pure curcumin. Additionally, in vivo studies showed that Alg@Cur@Se@ZIF-8 dramatically reduced tumour growth compared to free curcumin in 4T1 tumour-bearing mice. More importantly, the histological study confirmed that the developed drug delivery system successfully inhibited lung and liver metastasis while causing negligible toxicity in vital organs. Overall, due to the excellent inhibitory activity on cancerous cell lines and tumour-bearing animals, Alg@Cur@Se@ZIF-8 can be considered promising for breast cancer therapy.

Preparation and properties of bimetallic Co/Cu ZIF-67 for electrochemical application

Efforts to enhance the electrochemical properties of materials have become the focus of numerous studies because these properties are essential in various fields of application. Zeolitic imidazole framework-67 (ZIF-67) is a type of metal-organic framework (MOFs) expected to demonstrate excellent performance in electrochemical applications due to its numerous distinct properties. Consequently, various strategies and techniques have been developed to improve the electrochemical performance of ZIF-67. In this study, we employed bimetallic ZIF-67 constructed with cobalt (Co) and copper (Cu) metal ions within the imidazole frameworks. The use of bimetal is expected to increase conductivity and fine-tune the physicochemical properties of ZIF-67. Using coprecipitation methods, we synthesized both single-metal and bimetallic ZIF-67 and compared their characterizations. The addition of Cu metal ions does not alter the materials phase, ensuring compatibility with the single-metal ZIF-67 structure. However, the rhombic dodecahedron morphology of ZIF-67 shifts from a smooth to a concave and rough surface in Co/Cu ZIF-67. Furthermore, Co/Cu ZIF-67 exhibits higher peak current on their cyclic voltammetry (CV) curve by 46.15 µA. The results effectively illustrate the advantages of bimetal on ZIF-67 properties and performance. Finally, this study succesfully briefly demonstrate the potential development of Co/Cu-based ZIF-67 for various electrochemical applications.

Design yolk-shelled FeCo layered double hydroxide via a “one-stone-two-birds” strategy for oxygen evolution reaction

In order to meet the demands for green and sustainable energy, it is imperative to develop high-performance, cost-effective, and environmentally friendly electrocatalysts to enhance the oxygen evolution reaction (OER). In this regard, we introduce a novel reconstruction strategy, involving crystallization, growth, and etching processes, to synthesize a highly efficient electrocatalyst for the OER. A hydrothermal process was initially employed to synthesize materials of institute Lavoisier framework-88 (MIL-88) as a self-engaged precursor, which was subsequently transformed into hierarchical FeCo layered double hydroxide (LDH)@zeolitic imidazolate framework-67 (ZIF-67). Additionally, a “one-stone-two-birds” strategy was employed to create the yolk-shelled FeCo-LDH composite (denoted as YS FeCo-LDH) by etching FeCo-LDH@ZIF-67. On one hand, ZIF-67 can be gradually etched by the H+ ions generated through the hydrolysis of [Fe(C2O4)3]3−. On the other hand, simultaneously released Fe3+ and Co2+ co-precipitate with OH–/C2O42−, resulting in the formation of the FeCo-LDH shells. Benefiting from the yolk-shell structure, excellent microstructural integrity, efficient mass transport within interlinked nanocages, and abundant active sites, the YS FeCo-LDH catalyst exhibits remarkable electrocatalytic performance in the OER. This work represents a significant advancement in the development of high-efficiency yolk-shelled hollow electrocatalysts.

Tetracycline decontamination from aqueous media using nanocomposite adsorbent based on starch-containing magnetic montmorillonite modified by ZIF-67

In the present study, starch/zeolitic imidazole framework-67 (ZIF-67) modified magnetic montmorillonite nanocomposite adsorbent to remove tetracycline (TC) as an emerging antibiotic-based contaminant from aqueous media. The surface properties of the adsorbents were investigated using FTIR, XRD, SEM, EDX-Map, XPS, TEM, BET, and VSM analysis. The specific surface area of MMT, St/MMT-MnFe2O4, and St/MMT-MnFe2O4-ZIF-67 magnetic nanocomposite samples were found to be 15.63, 20.54, and 588.41 m2/g, respectively. The influence of pH, adsorbent amount, initial TC concentration, temperature, contact time, and coexisting ions on TC elimination was explored in a batch adsorption system. The kinetic and equilibrium data were well matched with the pseudo-second-order and Langmuir isotherm models, respectively. The maximum monolayer adsorption capacities of TC were obtained to be 40.24, 66.1, and 135.2 mg/g by MMT, St/MMT-MnFe2O4, and St/MMT-MnFe2O4-ZIF-67 magnetic nanocomposite adsorbents, respectively. Also, thermodynamic studies illustrated that the TC adsorption process is exothermic and spontaneous. Furthermore, the magnetic nanocomposite adsorbent St/MMT-MnFe2O4-ZIF-67 showed good reusability and could be recycled for up to five cycles. This excellent adsorption performance, coupled with the facile separation of the magnetic nanocomposite, gave St/MMT-MnFe2O4-ZIF-67 a high potential for TC removal from aqueous media.

Synergistic effect between adsorption and Fenton-like degradation on CoNiFe-LDH/ZIF-8 composite for efficient degradation of doxycycline

This study aimed to remove doxycycline (DC) from wastewater via a synergistic effect between adsorption and Fenton-like degradation processes. For this purpose, cobalt–nickel-iron-layered double hydroxide/zeolitic imidazolate framework-8 (CoNiFe-LDH/ZIF-8) was designed to have a continuous redox cycle between the transition metals of CoNiFe-LDH. Furthermore, a high adsorption capacity is provided mainly by ZIF-8, which also endows electrons to the reduced metals of LDH via zinc-oxygen-metal (Zn-O-M) bonds. The morphology, chemical structure, surface charge, and crystallinity of CoNiFe-LDH/ZIF-8 were investigated. The adsorption percentage of DC onto CoNiFe-LDH/ZIF-8 was estimated to be 45.62 %, while the degradation percentage reached 98.5 % after 90 min. The removal mechanism was proposed based on the experimental results, Zeta Potential, and X-ray photoelectron spectroscopy (XPS) analyses. In addition, Liquid Chromatography-Mass Spectrometry predicted the degradation pathways and the formed byproducts. Based on the promising reusability of CoNiFe-LDH/ZIF-8, it could be applied in industrial applications.