Core-shell Metal-organic Framework Research Articles

Combination of core-shell structured NH2-UiO-66@ZIF-8 loaded Ru (bpy)3 2+ and molecularly imprinted copolymer for the sensitive ECL detection of tetracycline.

A molecularly imprinted electrochemiluminescent sensor is developed for the sensitive detection of tetracycline in environmental and food samples. The sensor uses an ionic liquid (i.e. [APMIM]Br) modified graphene-carbon nanotube composite (GMI) material as substrate, a double-layered core-shell metal-organic framework NH2-UiO-66@ZIF-8 (NUZ) loaded bipyridyl ruthenium (NUZ@Ru) as luminescent material, and a molecularly imprinted copolymer of o-phenylenediamine and hydroquinone as recognition element. The ionic liquid-modified graphene-carbon nanotube composite has a favorable three-dimensional structure, high specific surface area, and good hydrophilicity; the core-shell structured metal-organic framework has high stability and plentiful reaction sites for loading; the molecularly imprinted copolymer film has enhanced stability and recognition effect. Hence, the resulting sensor combines the merits of several materials and presents improved performance. Under the optimum detection conditions, it shows a wide linear range of 0.05 µM - 1 mM, a low detection limit of 20 nM, high selectivity, and excellent stability. It has been successfully applied to the detection of tetracycline in different samples.

Structurally ordered core-shell MOFs in mixed matrix membrane as magnetic sieves for O2/N2 separation

Membrane separation technology has broad application prospects in O2/N2 separation, and improving the permselectivity of membranes remains a key problem to be solved. O2 and N2 have different magnetic properties and can be separated by magnetism. In addition, coupling magnetic separation with the use of a molecular sieve supported by metal-organic frameworks (MOFs) could further enhance the separation ability. In this work, a magnetic core-shell MOF (Fe3O4@ZIF-8) was prepared as a filler, and the impacts of the Fe3O4@ZIF-8 morphology, loading, channel magnetic properties and ordered arrangement on membrane O2/N2 selectivity were evaluated. To establish a magnetic-sieving O2 permeation channel, the preparation process was carried out in a magnetic field so that the fillers in the membrane were arranged orderly. Due to the synergistic impact of the structurally ordered MOF channel and magnetism, the gas transport performance of the resulting magnetic mixed matrix membranes (MMMs) was substantially improved. Therefore, the O2 permeability and O2/N2 selectivity of the 15 wt%Fe3O4@ZIF-8-8/Pebax MMMs reached 194 Barrer and 11.97, respectively. This study not only presents a novel approach for creating high-performance O2/N2 membranes but also plays a leading role in the development of magnetism-controlled multiscale (magnetic core-shell and filler-ordered) membrane structural engineering.

Anisotropic Interface Successive Assembly for Bowl-Shaped Metal-Organic Framework Nanoreactors with Precisely Controllable Meso-/Microporous Nanodomains.

Colloidal metal-organic framework (MOF) nanoparticles, with tailored asymmetric nanoarchitectures and hierarchical meso-/microporosities, have significant implications in high-performance nanocatalysts, nanoencapsulation carriers, and intricate assembly architectures. However, the methodology that could achieve precise control over the anisotropic growth of asymmetric MOF particles with tailored distributions of meso- and microporous regions has not yet been established. In this study, we introduce a facile anisotropic interface successive assembly approach to synthesize asymmetric core-shell MOF (ZIF-67) nanobowls with worm-like mesopores in the core and intrinsic micropores in the shell. Our synthesis pathway relies on anisotropic nucleation of mesoporous MOF nanohemispheres on emulsion interfaces through the cooperative assembly of surfactants and MOF precursors. This is followed by the growth of microporous MOF layers on both interfaces of mesoporous cores and emulsion droplets, resulting in a hierarchically porous core-shell nanostructure. By utilizing this multi-interface-driven approach, we enable the creation of diverse geometries and distributions of mesopores and micropores in asymmetric MOF nanoarchitectures. The obtained bowl-like meso-/microporous core-shell ZIF-67 particles exhibit enhanced catalytic activity for CO2 cycloaddition, attributed to reactant accumulation within the bowl-like architecture, active site accessibility in the open mesoporous core, and improved structural stability. Overall, our study provides insights and inspiration for exploring the intricate asymmetric nanostructures of hierarchically porous MOFs with diverse potential applications.

Symmetry-Mismatched SBU Transformation in MOFs: Postsynthetic Metal Exchange from Zn to Fe and Its Effects on Gas Adsorption and Dye Selectivity.

This research explores the alteration of metal-organic frameworks (MOFs) using a method called postsynthetic metal exchange. We focus on the shift from a Zn-based MOF containing a [Zn4O(COO)6] secondary building unit (SBU) of octahedral site symmetry (ANT-1(Zn)) to a Fe-based one with a [Fe3IIIO(COO)6]+ SBU of trigonal prismatic site symmetry (ANT-1(Fe)). The symmetry-mismatched SBU transformation cleverly maintains the MOF's overall structure by adjusting the conformation of the flexible 1,3,5-benzenetribenzoate linker to alleviate the framework strain. The process triggers a decrease in the framework volume and pore size alongside a change in the framework's charge. These alterations influence the MOF's ability to adsorb gas and dye. During the transformation, core-shell MOFs (ANT-1(Zn@Fe)) are formed as intermediate products, demonstrating unique gas sorption traits and adjusted dye adsorption preferences due to the structural modifications at the core-shell interface. Heteronuclear clusters, located at the framework interfaces, enhance the heat of CO2 adsorption. Furthermore, they also influence the selectivity of the dye size. This research provides valuable insights into fabricating novel MOFs with unique properties by modifying the SBU of a MOF with flexible organic linkers from one site symmetry to another.

One-Pot Synthesis of MOF@MOF: Structural Incompatibility Leads to Core-Shell Structure and Adaptability Control Makes the Sequence.

Core-shell metal-organic frameworks (MOF@MOF) are promising materials with sophisticated structures that cannot only enhance the properties of MOFs but also endow them with new functions. The growth of isotopic lcore-shell MOFs is mostly limited to inconvenient stepwise seeding strategies with strict requirements, and by far one-pot synthesis is still of great challenge due to the interference of different components. Through two pairs of isoreticular MOFs, it reveals that the structural incompatibility is a prerequisite for the formation of MOFs@MOFs by one-pot synthesis, as illustrated by PMOF-3@HHU-9. It further unveils that the adaptability of the shell-MOF is a more key factor for nucleation kinetic control. MOFs with flexible linkers has comparably slower nucleation than MOFs with rigid linkers (forming PMOF-3@NJU-Bai21), and structural-flexible MOFs built by flexible linkers show the lowest nucleation and the most adaptability (affording NJU-Bai21@HHU-9). This degree of adaptability variation controls the sequence and further facilitates the synthesis of a first triple-layered core-shell MOF (PMOF-3@NJU-Bai21@HHU-9) by one-pot synthesis. The insight gained from this study will aid in the rational design and synthesis of other multi-shelled structures by one-pot synthesis and the further expansion of their applications.

Enhanced sonophotocatalytic degradation of amoxicillin antibiotics using Fe3O4@SiO2/PAEDTC surrounded by MIL-101(Fe) in aquatic environment under the COVID-19 pandemic

In the conditions of corona disease, the need for antibiotics in the world has quadrupled, so it is required to remove their residues from the environment. A core–shell metal–organic framework (MOF) composed of Fe3O4, SiO2, and MIL-101 was synthesized by hydrothermal method and used as a sonophotocatalyst for the amoxicillin (AMX) degradation from aqueous solution. The features of the new MOF were determined by SEM, TEM, XRD, FTIR, and BET techniques. The specific area of core–shell magnetic particles was 992 m2/g, which was indicative of its usability to adsorb pollutants and photons. Complete degradation of AMX was achieved by sonophotocatalysis process based on prepared nanocomposite at pH of 5, UV intensity of 36 W, AMX concentration of 50 mg/L, US frequency of 36 kHz, and time of 25 min. Kinetic study with pseudo-first order reaction for the decomposition of AMX showed the order of kinetic constant rate as Ksonophotocatalytic > Kphotocatalytic > Ksonocatalytic > Kadsorption. Hydroxyl radicals (•OH) and holes (h+) were respectively determined as the main species in the decomposition of AMX by performing quenching experiments. Less than an 8% reduction in AMX degradation rate was observed by the sonophotocatalytic process in the presence of prepared nanocomposite during six consecutive reaction cycles. Removal rates of TOC > 77% and BOD5/COD ratio > 0.4 showed that AMX was converted to CO2, H2O, and simple degradable compounds during the sonophotocatalysis process. A toxicity study with the microbial culture of Escherichia coli (E. coli) demonstrated a lower inhibition rate in the sonophotocatalytic process compared to photolysis and photocatalytic processes. All the laboratory results proved that the Fe3O4@SiO2@MIL-101(Fe) is an encouraging candidate for AMX degradation to preserve the ecosystem.

Construction of Ce-MOF@COF hybrid nanostructure with controllable thickness for the electrochemical sensitive detection of metol

Covalent organic frameworks (COFs), a newly emerging kind of porous material, have gained extensive attention due to their fascinating structural features. However, the superiority of COFs as electrochemical sensing materials has not yet been adequately explored. Herein, a new type of core–shell metal–organic framework (MOF)@COF composites are synthesized through in situ growth of TAPB-DMTP-COF on the pre-synthesized Ce-BDC core. The thickness of the COF shell can be controlled to 20–50 nm by adjusting the Ce-MOF mass. It is found that the obtained MOF@COF composite possesses a larger electrochemical active area and faster electron transfer kinetic than its single component. As a case application of this composite, it has been employed as a sensing material for voltammetric detection of metol, where a linear range from 0.1 − 200 μM and a detection limit of 30 nM have been obtained. This study provides a new strategy to synthesize COF-based electrode materials as well as to explore their electrochemical properties and applications.

Trimetallic MOFs-derived Fe-Co-Cu oxycarbide toward peroxymonosulfate activation for efficient trichlorophenol degradation via high-valent metal-oxo species

Advanced oxidation processes based on high-valent metal species have attracted much attention due to their high reactivity and selectivity in degrading refractory organic pollutants, but the preparation of such catalysts remains a great challenge. Herein, FeCoCu-nitrogen-doped carbon (FeCoCu-NC), a trimetallic catalyst capable of producing high-valent metal species, was synthesized by direct carbonization of core–shell Metal-organic frameworks (MOFs). The rationally designed catalyst exhibited high catalytic activity in wide pH range and high resistance to common radical scavengers, anions and natural organics. The incorporation of Cu in FeCoCu-NC (TNCX) not only enhanced the catalytic activity but also changed the activation mechanism of peroxymonosulfate (PMS) from a radical pathway to a non-radical pathway dominated by high-valent metal species. In addition, the TNC5/PMS system showed higher trichlorophenol (TCP) removal efficiency and PMS utilization compared to the radical-dominated FeCo-NC/PMS system and the 1O2-dominated CoCu-NC/PMS system. This study provides a facile strategy to the preparation of advanced catalysts from multi-metal MOFs and is expected to provide guidance for the design of heterogeneous high-valent metal catalysts.

Implementation of a Core-Shell Design Approach for Constructing MOFs for CO2 Capture.

Adsorption-based capture of CO2 from flue gas and from air requires materials that have a high affinity for CO2 and can resist water molecules that competitively bind to adsorption sites. Here, we present a core-shell metal-organic framework (MOF) design strategy where the core MOF is designed to selectively adsorb CO2, and the shell MOF is designed to block H2O diffusion into the core. To implement and test this strategy, we used the zirconium (Zr)-based UiO MOF platform because of its relative structural rigidity and chemical stability. Previously reported computational screening results were used to select optimal core and shell MOF compositions from a basis set of possible building blocks, and the target core-shell MOFs were prepared. Their compositions and structures were characterized using scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. Multigas (CO2, N2, and H2O) sorption data were collected both for the core-shell MOFs and for the core and shell MOFs individually. These data were compared to determine whether the core-shell MOF architecture improved the CO2 capture performance under humid conditions. The combination of experimental and computational results demonstrated that adding a shell layer with high CO2/H2O diffusion selectivity can significantly reduce the effect of water on CO2 uptake.

Integrating Ultrasmall Pd NPs into Core–Shell Imidazolate Frameworks for Photocatalytic Hydrogen and MeOH Production

The construction of photoactive units in the proximity of a stable framework support is one of the promising strategies for uplifting photocatalysis. In this work, the ultrasmall Pd NPs implanted onto core-shell (CS) metal organic frameworks (MOFs), i.e., CS@Pd nanoarchitectures with tailored electronic and structural properties are reported. The all-in-one heterogeneous catalyst CS@Pd3 improves the surface functionalities and exhibits an outstanding hydrogen evolution reaction (HER) activity rate of 12.7 mmol g-1 h-1, which is 10-folds higher than the pristine frameworks with an apparent quantum efficiency (AQE) of 9.02%. The bifunctional CS@Pd shows intriguing results when subjected to photocatalytic CO2 reduction with an impressive rate of 71 μmol g-1 h-1 of MeOH under visible-light irradiation at ambient conditions. Spectroscopic data reveal efficient charge migrations and an extended lifetime of 2.4 ns, favoring efficient photocatalysis. The microscopic study affirms the formation of well-ordered CS morphology with precise decoration of Pd NPs over the CS networks. The significance of active Pd and Co sites is addressed by congruent charge-transfer kinetics and computational density functional theory calculations of CS@Pd, which validate the experimental findings with their synergistic involvement in improved photocatalytic activity. This present work provides a facile and competent avenue for the systematic construction of MOF-based CS heterostructures with active Pd NPs.

Enhancing hydrophobicity via core–shell metal organic frameworks for high-humidity flue gas CO2 capture

Developing metal–organic framework (MOF) materials with the moisture-resistant feature is highly desirable for CO2 capture from highly humid flue gas. In this work, a new core–shell MOF@MOF composite using Mg-MOF-74 with high CO2 capture capacity as a functional core and hydrophobic zeolitic imidazolate framework-8 (ZIF-8) as a protective shell is fabricated by the epitaxial growth method. Experimental results show that the CO2 adsorption performance of the core–shell structured Mg-MOF-74@ZIF-8 composites from water-containing flue gas is enhanced along with their improved hydrophobicity. The dynamic breakthrough results show that the Mg-MOF-74@ZIF-8 with three assembled layers (Mg-MOF-74@ZIF-8-3) can capture 3.56 mmol·g−1 CO2 from wet CO2/N2 (VCO2: VN2 = 15:85) mixtures, which outperforms Mg-MOF-74 (0.37 mmol·g−1) and most of the reported physisorbents.

UiO‐66‐NH2@67 Core–Shell Metal–Organic Framework as Fillers in Solid Composite Electrolytes for High‐Performance All‐Solid‐State Lithium Metal Batteries

Benefiting from employing solid composite electrolytes (SCEs), all‐solid‐state lithium‐ion batteries (ASSLBs) are recognized to occupy with high energy density and safety. Herein, a polymer‐based SCE membrane (SCE‐66@67) with core–shell structured metal–organic frameworks (MOFs) (UiO‐66‐NH2@67) as the fillers is presented. The SCE has combined the advantages of the two kinds of MOFs and shows a satisfying ionic conductivity (2.09 × 10−4 S cm−1 at 60 °C) and a wide electrochemical stability window of ≈5.0 V. The full cell (Li/SCE‐66@67/LiFePO4) also maintains a high capacity of 120.9 mAh g−1 at 3 C. This research might help to promote the development of future SCEs for ASSLBs.

Synthesis of Single-Crystalline Core-Shell Metal-Organic Frameworks.

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. However, the synthesis of single-crystalline core-shell MOFs is very challenging, and thus a limited number of examples have been reported. Here, we suggest a method of synthesizing single-crystalline HKUST-1@MOF-5 core-shells, which is HKUST-1 at the center of MOF-5. Through the computational algorithm, this pair of MOFs was predicted to have the matched lattice parameters and chemical connection points at the interface. To construct the core-shell structure, we prepared the octahedral- and cubic-shaped HKUST-1 crystals as a core MOF, in which the (111) and (001) facets were mainly exposed, respectively. Via the sequential reaction, the MOF-5 shell was well-grown on the exposed surface, showing a seamless connect interface, which resulted in the successful synthesis of single-crystalline HKUST-1@MOF-5. Their pure phase formation was proved by optical microscopic images and powder X-ray diffraction (PXRD) patterns. This method presents the potential of and insights into the single-crystalline core-shell synthesis with different kinds of MOFs.

A Strategy for the Determination of Alkaline Phosphatase Based on the Self-Triggered Degradation of Metal-Organic Frameworks by Phosphate.

Alkaline phosphatase (ALP) is widely present in the human body and is an important biomarker. Numerous ALP detection studies have been carried out, and ascorbic acid (AA) is often used as the reducing component in the sensors to monitor ALP levels since it can be produced from ascorbic acid 2-phosphate (AA2P) hydrolysis in the presence of ALP. However, it is well-known that AA is a strong reducing agent and can be easily oxidized. The disproportion between oxidized AA and reduced AA reactions results in the generation of AA free radicals with single electrons that may lead to inaccurate results in assays. To solve this problem, we synthesized a core-shell metal-organic framework sensor (PATP-Au@ZIF-8 NP) and used it as a sensitive and accurate ALP detection sensor with self-triggered control of phosphate ions (Pi) to avoid the potential inaccuracy of the method that uses AA as the reducing component. By establishing a physical shell on the surface of the gold nanoparticles (Au NPs), the sensor not only can eliminate the random assembly of metal nanoparticles caused by plasma exposure but also can generate self-triggering of Pi caused by ALP. Pi can decompose ZIF-8 through coordination with Zn2+ and thus can destroy the ZIF-8 shell structure of the prepared PAZ NPs. Au NPs are released and then become aggregated, in turn causing the SERS "hot spot" area to increase. The enhancement of the SERS signals was found to be directly associated with the level of Pi released from ALP-triggered hydrolysis. The response of the strategy was linear at ALP concentrations ranging from 0.1 to 150 mU/mL (r = 0.996) with a detection limit of 0.03 mU/mL. Lastly, the developed strategy was employed in the evaluation of ALP inhibitors, and the possibility to implement the developed SERS strategy for rapid and selective analysis of ALP in human serum was demonstrated.

ZIF-8@Zn-MOF-74 core–shell metal–organic framework (MOF) with open metal sites: Synthesis, characterization, and gas adsorption performance

In this paper, an efficient hierarchical metal–organic framework (MOF), namely ZIF-8@Zn-MOF-74 with core–shell structure and coordinately open/unsaturated metal sites (OMS) was successfully synthesized. For this purpose, the facile post-synthetic ligand exchange (PSE) method at ambient temperature was applied. In the fabricated core–shell porous structure, the SOD-type ZIF-8 acts as the core, providing molecular sieving features, resulting in greater adsorption selectivity values. On the other hand, Zn-MOF-74 as the shell part, owing to the larger pore size, makes entrance and diffusion of the guest gas molecules more convenient. In addition, due to the presence of OMS in the Zn-MOF-74 structure, a greater adsorption capacity would be achieved. The prepared MOFs were characterized by FESEM, EDS, HRTEM, FTIR, XRD, BET, and TGA analyses, and formation of the core–shell structure was confirmed. The FESEM and HRTEM images demonstrated rather smooth coverage of the core (ZIF-8) with a layer of the shell (Zn-MOF-74). The rather high BET surface area (633.2 m2/g) and total pore volume (0.671 cm3 g−1) of the core–shell structure, make it promising for gas adsorption applications. The gas adsorption measurements were conducted for CO2, N2, H2, O2, CH4, C2H6, C3H8, C2H4, and C3H6 pure gases at 308 K and equilibrium pressures up to 4 bar. It was found that the CO2 adsorption capacity of ZIF-8@Zn-MOF-74 nanoparticles (3.27 mmol g−1) has enhanced ∼63.5 % compared to the pristine ZIF-8 (∼2 mmol/g). The CO2/N2 and CO2/CH4 selectivity values were also increased by 85.4 % and 74.4 %, respectively, that indicates overcoming the trade-off between adsorption capacity and selectivity.

Facile synthesis of Ag/ZIF-8@ZIF-67 as an electrochemical sensing platform for sensitive detection of halonitrophenols in drinking water.

Halonitrophenols (HNPs) are an emerging type of aromatic disinfection byproduct, with detected concentrations of ∼nmol L-1 in source water and drinking water. Currently, there are no standard methods for identifying HNPs, and most of the reported methods are time-consuming and equipment-dependent. A core-shell metal-organic framework (MOF) based electrochemical sensor (Ag/ZIF-8@ZIF-67) capable of detecting 2,6-dichloro-4-nitrophenol (2,6-DCNP) is reported in this study. The electrochemical sensor obtains the concentration of 2,6-DCNP by detecting the peak current passing through the sensor. In this sensor, Ag nanoparticles (AgNPs) play a key role in electrochemical sensing by reducing nitro groups via electron transfer, and porous structure with a large surface area is offered by ZIF-8@ZIF-67. The cyclic voltammetry (CV) response of Ag/ZIF-8@ZIF-67 was found to be approximately 1.75 times and 2.23 times greater than that of Ag/ZIF-8 and Ag/ZIF-67, respectively, suggesting an ideal synergistic effect of the core-shell structures. The Ag/ZIF-8@ZIF-67 sensor exhibited exceptional sensitivity to 2,6-DCNP, exhibiting a broad linear response range (R2 = 0.992) from 240 nmol L-1 to 288 μmol L-1 and a low detection limit of 20 nmol L-1. Furthermore, the sensor exhibited good anti-interference for isomers and common distractors in water, excellent stability and reproducibility, and high recovery in actual water samples. Our reported sensor gives a novel strategy for sensitive, selective, and in situ detection of 2,6-DCNP in practical analysis.

Covalently connected core–shell NH2-MIL-125@COFs-OH hybrid materials for visible-light-driven CO2 reduction

Herein, the covalently connected core–shell metal–organic frameworks (MOFs)@covalent-organic frameworks (COFs) hybrid materials were successfully constructed by coating the stable COF-OH shell on the NH2-MIL-125 core. The introduction of the NH2-MIL-125 core endowed the hybrid materials with high Brunauer–Emmett–Teller (BET) surface area (SBET) and abundant unsaturated metal sites. And the coating of COF-OH shell endowed the hybrid materials outstanding physicochemical stability and visible-light response, and suitable band gaps. Moreover, the thickness of the COF-OH shell was carefully adjusted according to the feeding amount of NH2-MIL-125. Impressively, the electron transfer pathway in the formed heterostructure was clarified and it was proven that a type-II heterojunction was generated between the MOFs and the COFs. The formed stable CN covalent bonds in the interfacial layer was beneficial to the photogenerated electron transfer and the electron-hole pairs separation, which greatly enhanced the CO2 photocatalytic reduction. The product NH2-MIL-125@COF-3 exhibited the highest CO yield of 22.93 μmol·g−1·h−1, about 2 times higher than NH2-MIL-125 (11.82 μmol·g−1·h−1) and 3 times greater than COF-OH (7.26 μmol·g−1·h−1). This work can provide helpful ideas for the careful design of the novel MOFs@COFs hybrid materials as well as useful exploration for the CO2 photocatalytic reduction.

Synthesis, characterization, and gas adsorption performance of an efficient hierarchical ZIF-11@ZIF-8 core–shell metal–organic framework (MOF)

In this paper, the solvent-assisted linker exchange (SALE) technique was successfully applied for the synthesis of porous ZIF-11@ZIF-8 core–shell composite structure metal–organic framework (MOF). The RHO-type ZIF-11 owing to larger cavities along with higher freedom in linker rotation, acts as the core and contributes in adsorption capacity enhancement. On the other hand, the SOD-type ZIF-8 provides greater molecular sieving features due to its lower degree of linker flexibility and thereby results in an improvement of the adsorption selectivity. The morphology and structure of the fabricated MOFs were characterized by XRD, FTIR, FESEM, EDS, TEM, BET, and TGA analyses and formation of the core–shell structure was confirmed. The BET surface area and micropore volume of the synthesized ZIF-11@ZIF-8 MOF were obtained as high as 1023.4 m2/g and 0.435 cm3 g−1, respectively. Gas adsorption measurements were carried out for CO2, N2, CH4, C2H6, and C2H4 gases at 298 and 328 K and equilibrium pressures up to 4 bar. The results revealed a remarkable rise (∼100 %) in CO2 adsorption capacity of ZIF-11@ZIF-8 nanoparticles (8.21 mmol g−1), compared to the pristine ZIF-11 (4.35 mmol g−1) at 298 K. The CO2/N2 and CO2/CH4 adsorption selectivity values were also augmented by 131 % and 92 %, respectively. In addition, the fabricated core–shell MOF, exhibited greater ethane (C2H6) adsorption capacity by ∼ 65 %, along with ethane to ethylene (C2H4) adsorption selectivity enhancement by ∼ 50 %. The higher adsorption capacity values without sacrificing adsorption selectivity suggests that the controlled core–shell MOF structures would be promising candidates for effective separation of CO2 from CH4 and N2 as well as C2H6 from C2H4.

Nitrogen-Doped Carbon Dots in Zeolitic Imidazolate Framework Core-Shell Nanocrystals: Synthesis and Characterization

Metal-organic frameworks (MOFs) have exciting properties and promising applications in different fields. In this work, novel zeolitic imidazolate frameworks (ZIFs) have been synthesized by encapsulating N-doped carbon quantum dots (N-CDs) with a blue FL into the zeolitic imidazolate framework materials core-shell structure (ZIF-8@ZIF-67). The functionalized core-shell MOFs maintained their crystal structure, morphology, and enhanced UV-vis absorbance. The properties of these new composites exhibit excellent potential for different applications including sensing, photo-catalysis, and selective adsorption.

Preparation of metal–organic framework @molecularly imprinted polymers for extracting strobilurin fungicides from agricultural products

The core–shell metal–organic framework coated with molecularly imprinted polymers (ZIF-8@MIPs) were successfully synthesized by surface imprinting technique, and applied as adsorbents for solid-phase extraction of strobilurin fungicides. The obtained hybrid complex was characterized in detail, and their adsorbing and recognition performance were evaluated. The results showed that ZIF-8@MIPs presented typically core–shell structure with MIP shell (about 20 nm), and exhibited larger adsorption capacity (102.5 mg g−1) and fast adsorption ability (only 5 min). Under the optimized conditions, a sensitive, efficient and reliable method for determining six strobilurin fungicides in different agricultural products based on ZIF-8@MIPs coupling with high performance liquid chromatography-tandem mass spectrometry was established. This method showed good linearity with correlation coefficients higher than 0.9990. With spiked at three different concentration levels in agricultural products (apple, pear, banana, Chinese cabbage, cabbage, cucumber), the good recoveries (83.5–129.0%) with relative standard deviations from 0.5 to 10.2% were obtained. The limit of detections and the limit of quantifications were 0.01–1.12 ng g−1 and 0.03–3.73 ng g−1, respectively. Those results demonstrated good potential application of ZIF-8@MIPs for enriching and separating trace strobilurin fungicides in agricultural samples.