Bimetallic Zeolitic Imidazolate Framework Research Articles

Bimetal Metal‐Organic Frameworks Derived Hierarchical Porous Cobalt@Nitrogen‐Doped Carbon Tubes as An Efficient Electrocatalyst for Oxygen Reduction Reaction

AbstractThe design and preparation of inexpensive, stable, and superior catalysts for the oxygen reduction reaction (ORR) are significant but challenging towards sustainable energy conversion technologies. Herein, a tubular template‐assisted strategy for fabrication of cobalt nanoparticles (Co NPs) embedded in one‐dimensional (1D) N‐doped porous tubular carbon composites (Co@N−CTs) is developed via in‐situ growth of bimetallic zeolitic imidazolate frameworks (ZnCo−ZIFs) on hollow polypyrrole (PPy) nanotubes surface. The PPy can not only act as a hollow tubular template, but also efficiently inhibit aggregation of Co NPs. Thanks to the 1D tubular interconnected networks and abundant micro‐/nano‐ porous tube wall structure, the as‐prepared Co@N−CTs catalyst achieves outstanding ORR performance with an onset potential (E0) of 0.982 V and a half‐wave potential (E1/2) of 0.864 V. Meanwhile, the Co@N−CTs catalyst also demonstrates superior durability with slightly decay of 3 % of initial current over 40000 s, as well as tolerance to the methanol. Furthermore, the Co@N−CTs cathode exhibits a large specific capacity (784 mAh g−1) and satisfying power density (116 mW cm−2) in a Zn‐air battery.

Bimetallic zeolitic imidazolate framework derived magnetic catalyst for high-efficiency CO2 chemical fixation

Metal-organic framework (MOF) derived porous carbons are known as desirable catalysts for carbon dioxide (CO2) catalytic conversion. However, practical CO2 utilization processes are severely hampered by their powder form and relatively poor activities. Herein, we demonstrate the rational synthesis of ZnO and/or metallic Co embedded in N-doped porous carbon by one-step pyrolysis of bimetallic MOF, Co/Zn-ZIF. The optimized catalyst exhibits remarkable activity and recyclability towards the coupling reaction of CO2 and epoxides owing to hierarchical pore, good CO2 uptake and sufficient active sites. More importantly, its catalytic performance can be well maintained even under dilute CO2 (15%), humid environment or light irradiation instead of heating. These results pave a way to develop highly efficient materials for practical CO2 catalytic conversion.

Enhanced catalytic elimination of typical VOCs over ZnCoOx catalyst derived from in situ pyrolysis of ZnCo bimetallic zeolitic imidazolate frameworks

In this work, ZnCoOx catalysts were prepared using in situ pyrolysis of ZnCo bimetallic zeolitic imidazolate frameworks (ZIFs), which were rationally designed on the basis of a metal ion doping strategy. The derived Zn0.05CoOx with proper doping of Zn (Zn/Co molar ratio of 0.05) exhibited superior catalytic activity and durability towards catalytic elimination of different volatile organic compounds (VOCs) including benzene, toluene and cyclohexane under simulated real-exhaust conditions. Both Brønsted and Lewis acid sites were beneficial for cyclohexane degradation, whereas only Lewis acid sites were responsible for eliminations of benzene and toluene. In addition, the effect of chemical structures of VOCs on their catalytic elimination over Zn0.05CoOx was explored. Compared to benzene and toluene, cyclohexane molecule was more easily eliminated, attributed to strong adsorption onto catalyst and special chemical structure of cyclohexane. The obtained results can provide new strategy for rational design of highly efficient catalytic materials for eliminating VOCs.

Chain-tailed dodecahedron structure derived from Zn/Co-ZIFs/CNTs with excellent rate capability as an anode for lithium-ion batteries

Herein, a unique dodecahedron composite material of Zn-Co bimetallic zeolitic imidazolate frameworks (ZIFs) and carbon nanotubes (CNTs) is synthesized by a simple room temperature static precipitation-annealing process. As an anode material for lithium-ion batteries (LIBs), the designed nanomaterials exhibits excellent lithium storage performance and cycle performance. It demonstrates a high discharge specific capacity of 720.9 mAh g-1 at 100 mA g-1. Besides, a high reversible capacity of 608.7 mAh g-1 at a current density of 500 mA g-1 after 300 cycles. The significant improvement in the electrochemical performance of Zn/Co-ZIFs/CNTs nanocomposite can be attributed to the strong synergy between Zn/Co-ZIFs and CNTs.

Nitrogen-doped porous carbon derived from bimetallic zeolitic imidazolate frameworks for electrochemical Li+/Na+ storage

Porous carbon is regarded as one of the most promising anode candidates for Li-ion battery and Na-ion battery, and the specific porous structure and heteroatom doping within porous carbon play a key role in the electrochemical performance. We herein demonstrate a series of nitrogen-doped porous carbon (NPC) by simply carbonizing bimetallic ZnCo-containing zeolitic imidazolate frameworks (ZnCo-ZIFs). The nitrogen content, specific surface area, and microstructure of prepared NPCs are balanced by adjusting the Zn2+/Co2+ molar ratio of ZnCo-ZIFs and carbonization process parameters. The optimized NPC derived from ZnCo-ZIFs delivers high specific capacity of 876.5 and 352.6 mA h g−1 for Li+ storage at 0.1 and 5 A g−1, respectively. After repeating 500 cycles at a high current density of 1 A g−1, it almost has no capacity loss. In addition, the electrode also shows a great promise for Na+ storage. The excellent electrochemical Li+/Na+ storage performances could be attributed to the hierarchical porous structure, large specific surface area, and relatively high N-doping content.

Rational Design of Bimetallic Zeolitic Imidazolate Framework‐Derived C, N Dual‐Doped ZnO/Co for Boosting Lithium Storage

AbstractLithium‐ion batteries (LIBs) are the preeminent technology for energy storage, having the highest energy density for large‐scale commercial applications. Owing to üast assiduous studies, a good number of reported advanced anode materials possess excellent electrochemical properties. In this work, a porous C, N dual‐doped ZnO/Co composite is successfully prepared by metal–organic frameworks (MOF)‐template mediated synthesis method utilizing a self‐sacrificing template of bimetallic zeolitic imidazolate framework (denoted as ZnCo‐ZIF) and is tested as a lithium‐ion battery anode material. Due to the advantageous structural and morphological features, such as well‐defined open framework clusters with polyhedron crystal structure, conductive porous carbon network and synergistic effects, the as‐prepared C, N dual‐doped ZnO/Co electrode delivers a specific capacity of 800 mAh g‐1 at 0.2 A g‐1 for 500 cycles together with unprecedented cycling ability of 590 mAh g‐1 at 1 A g‐1 over 1000 cycles. Moreover, density functional theory (DFT) calculations demonstrate the relationship between the electronic structure and electrochemical activity of ZnO/Co anode material. These results show that the synthesized C, N dual‐doped ZnO/Co is a promising high‐performance anode material for LIBs.

A sensor array based on DNA-wrapped bimetallic zeolitic imidazolate frameworks for detection of ATP hydrolysis products.

Most current biosensors were designed for the detection of individual analytes, or a group of chemically similar analytes. We reason that sensors designed to track both reactants and products might be useful for following chemical reactions. Adenosine triphosphate (ATP) is a key biomolecule that participates in various biochemical reactions, and its hydrolysis plays a fundamental role in life. ATP can be converted to adenosine diphosphate (ADP) and inorganic phosphate (Pi) via the dephosphorylation process. ATP can also be hydrolyzed to adenosine monophosphate (AMP) and pyrophosphate (PPi) through depyrophosphorylation, depending on where the bond is cleaved. The detection of ATP-related hydrolysates would enable a better understanding of the different reaction pathways with a high level of robustness and confidence. Herein, we prepared a fluorescent sensor array based on a series of bimetallic zeolite imidazole frameworks M/ZIF-8 (M = Ni, Mn, Cu) and ZIF-67 to discriminate ATP hydrolysis and detect ATP hydrolysis related analytes. A fluorescently-labeled DNA oligonucleotide was used for signaling. Interestingly, Cu/ZIF-8 exhibited an ultrahigh selectivity for recognizing pyrophosphate with a detection limit of 2.5 μM. Moreover, the practicality of this sensor array was demonstrated in fetal bovine serum, clearly discriminating ATP hydrolysis products.

Mixed metal node effect in zeolitic imidazolate frameworks.

We synthesized two series of bimetallic (zinc and cobalt) zeolitic imidazolate frameworks (ZIF-62) under different solvothermal conditions. It is found that the structure of the derived ZIF crystals is highly sensitive to synthesis conditions. One series possesses the standard ZIF-62 structure, whereas the other has a mixed structure composed of both the standard structure and an unknown one. The standard series exhibits a slight negative deviation from linearity of melting temperature (Tm) and glass transition temperature (Tg) with the substitution of Co for Zn. In contrast, the new series displays a stronger negative deviation. These negative deviations from linearity indicate the mixed metal node effect in bimetallic ZIF-62 due to the structural mismatch between Co2+ and Zn2+ and to the difference in their electronic configurations. The new series involves both cobalt-rich and zinc-rich phases, whereas the standard one shows one homogeneous phase. Density functional theory calculations predict that the substitution of Co for Zn increases the bulk modulus of the ZIF crystals. This work indicates that the structure, melting behaviour, and mechanical properties of ZIFs can be tuned by metal node substitution and by varying the synthetic conditions. Both series of ZIFs have higher glass forming abilities due to their higher Tg/Tm ratios (0.77–0.84) compared to most good glass formers.

Designing bimetallic zeolitic imidazolate frameworks (ZIFs) for aqueous catalysis: Co/Zn-ZIF-8 as a cyclic-durable catalyst for hydrogen peroxide oxidative decomposition of organic dyes in water.

ZIF-8 is well known hybrid material that is self-assembled from inorganic and organic moieties. It has several potential applications due to its unique structure. One of these potential applications is in advanced oxidation processes (AOP) via a heterogeneous catalysis system. The use of modified ZIF-8/H2O2 for the destruction of the azo dye methyl orange (MO) is presented in this work to explore its efficacy. This work presents the bimetallic Co/Zn-ZIF-8 as an efficient catalyst to promote H2O2 oxidation of the MO dye. Co/Zn-ZIF-8 was synthesized through a hydrothermal process, and the pristine structure was confirmed using XRD, FTIR, and XPS. The Co/Zn-ZIF-8/H2O2 system successfully decolorized MO at the selected pH 6.5. It was found that more than 90% of MO (10 ppm) was degraded within only about 50 minutes. Proposed radical and redox mechanisms are presented for H2O2 decomposition where the redox mechanism is suggested to predominate via a Co(ii)/Co(iii) redox consecutive cyclic process.

Zeolitic imidazolate framework derived porous ZnO/Co3O4 incorporated with gold nanoparticles as ternary nanohybrid for determination of hydrazine

A sensing platform based on porous ZnO/Co3O4 is introduced for determination of hydrazine in alkaline media. The bimetallic oxides were prepared by calcination of bimetallic zeolitic imidazolate framework (Zn/CoZIF) as a sacrificial template. Zn/CoZIF and ZnO/Co3O4 were characterized via several techniques. The porous ZnO/Co3O4 was utilized to modify glassy carbon electrode (ZnO/Co3O4/GCE), followed by immobilization of Au nanoparticles (NPs) on its surface to prepare Au/ZnO/Co3O4/GCE. The electrode exhibited two linear ranges of 2–1900 μM and 1900–8500 μM with sensitivity of 0.058 and 0.048 μA μM−1 for determination of hydrazine in aqueous solution. The sensor showed remarkable lower oxidation potential and limit of detection rather than ZnO/Co3O4/GCE. Furthermore, the sensor displayed acceptable selectivity toward oxidation of hydrazine in the presence of some interfering species. The results confirm that Au/ZnO/Co3O4/GCE can be considered as sensitive and reliable sensor toward the oxidation of hydrazine due to the porous structure of ZnO/Co3O4, high conductivity of Au NPs, and the synergic effect among the constituents.

Metal Exchange of ZIF-8 and ZIF-67 Nanoparticles with Fe(II) for Enhanced Photocatalytic Performance.

Zeolitic imidazolate frameworks (ZIFs), such as ZIF-8 and ZIF-67, were found to be efficient catalysts. However, ZIFs are not used much in photocatalysis due to their low photocatalytic activity for most reactions. The photocatalytic activity can be improved by modifying the framework by exchanging the Zn(II) ions (ZIF-8) and Co(II) ions (ZIF-67) with a more photocatalytically active metal(II) ion to form an efficient bimetallic ZIF photocatalyst. Redox-active iron (Fe)-based materials are known to be highly potent photocatalysts. Thus, incorporating iron into ZIFs could significantly enhance their photocatalytic performance. In this study, we modified nanosized ZIF-8(Zn) and ZIF-67(Co) via metal (Fe2+) exchange to produce bimetallic frameworks that are photocatalytically more active than their parent ZIFs. Nanosized ZIF-8 and ZIF-67 were synthesized isothermally in either water or methanol under ambient conditions. From these, Fe-containing bimetallic ZIF-8 and ZIF-67 nanoparticles were synthesized via the metal exchange, and their performance on the photocatalytic degradation of dye was evaluated. The morphology and crystal structures of the pristine ZIF-8 and ZIF-67 nanoparticles were retained to a large extent during the iron exchange. Their Brunauer–Emmett–Teller (BET) surface areas decreased by less than 15% for nZIF-8 and less than 12% for nZIF-67. The binding energy values on X-ray photoelectron spectroscopy (XPS) confirmed the preservation of the oxidation state of Fe(II) during the exchange process. A remarkably higher catalytic activity was observed for the photocatalytic degradation of dye by the Fe-exchanged nZIF-8 and nZIF-67 compared to their parent ZIFs. This proved that the incorporation of Fe(II) centers into the ZIF framework enhanced the photocatalytic activity of the framework dramatically. In addition, these catalysts can be regenerated and reused without an appreciable loss in activity.

The intergrated nanostructure of bimetallic CoNi-based zeolitic imidazolate framework and carbon nanotubes as high-performance electrochemical supercapacitors

In this study, a series of one-dimensional (1D)/two-dimensional (2D) heterostructure hybrids were fabricated through the in situ growth of a Co and Ni bimetallic zeolitic imidazolate framework (CoNi-ZIF) around N-doped carbon nanotubes (N-CNTs). The hybrids were further exploited as effective supercapacitor materials. The N-CNTs were prepared by carbonizing a mixture of glucose and the melamine–cyanuric acid complex at a high temperature (900 °C) under N2 atmosphere and applied as the template for the in situ synthesis of CoNi-ZIF nanosheets (NSs). The 1D N-CNTs in the hybrids can act as the high-way for charge transfer to boost the faradaic reactions. Changing the usage of metal precursors not only provided abundant redox reaction sites in 2D CoNi-ZIF NSs but also modulated the microstructures and chemical components of the hybrids. The integration of the features of N-CNTs and CoNi-ZIF NSs can result in a synergistic effect between N-CNTs and CoNi-ZIF NSs. Therefore, the obtained CoNi-ZIFs and N-CNTs hybrid (CoNi-ZIF@N-CNT) exhibited superior electrochemical capacitive performance. Comparison revealed that the CoNi-ZIF@N-CNT-2 hybrid, which was prepared with a 1:1 mass ratio of Co(NO3)2·6H2O and Ni(NO3)2·6H2O, displayed the largest specific capacitance of 1118F g−1 at 1 A g−1, which was higher than the capacitance of most reported metal–organic framework (MOF)-based supercapacitor electrodes. Moreover, the asymmetric supercapacitor based on the CoNi-ZIF@N-CNT-2 electrode exhibited a high energy density of 51.1 Wh kg−1 at the power density of 860.1 W kg−1 and good cycle stability. This work can provide a facile and effective way for the fabrication of heterostructured 1D/2D nanostructures based on 2D MOFs for advanced energy storage.

ZIF-L Derived Bimetallic N-Doped Porous Carbon-Prussian Blue Composite as Efficient Catechol Electrochemical Sensor

The development of effective and accurate catechol (CC) electrochemical sensors is critical for environment and life health perspectives. A facile pyrolysis of 2D bimetallic (Zn/Co) zeolitic imidazolate framework (Zn/Co-ZIF-L) was employed to prepare Zn and Co nanoparticles encapsulated in N-doped porous carbon (Zn/Co@NPC). Prussian blue (PB) was synthesized in situ via the co-precipitation of ferricyanide ([Fe(CN)6]3−) and iron (II) ion originated from the reduction of Fe3+ by Zn/Co@NPC and then served as the main active substance of CC detection. The morphology and composition of the final composite Zn/Co@NPC-PB were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). The Zn/Co@NPC-PB modified glass carbon electrode (GCE) exhibits two concentration linear ranges of 4.13 μM − 1.08 mM (R2 = 0.999) and 1.08 mM−11.82 mM (R2 = 0.999) for CC electrochemical detection with a limit of detection 1.05 μM (S/N = 3). At the same time, the Zn/Co@NPC-PB/GCE shows great selectivity to electrochemical oxidation behavior of CC in presence of 20 folds dihydroxybenzene interferents such as hydroquinone and resorcinol. Furthermore, it showed a long-term stability and near 100% recovery for the detection of a real sample in Yellow River water.

Boosting electron transport over controllable N ligand doping for electrochemical conversion of CO2 to syngas

The Electrocatalytic CO2 reduction reaction provides a promising strategy for the preparation of syngas, which not only can reduce CO2 emissions to regulate global warming and solve the energy crisis, but also provide raw materials for the chemical industry to ease the energy crisis. However, it is extremely challenging to improve the catalytic activity of the electrocatalyst and regulate the ratio of CO and H2 in syngas. To solve the problem, nanomaterial Co-N-C-Ph derived from 1,10-phenanthroline doped bimetallic zeolitic imidazolate frameworks (B-ZIFs) was designed as electrocatalysts to produce syngas in the work. The electrocatalysts display 10.5 mA cm−2 of geometrical current density at -1.1 V (vs. RHE), with an approximately 3:2 ratios of CO/H2. The current density of generated CO current density and FECO, which could remain nearly unchanged after electrolyzing 16 h in CO2RR, revealing robust long-time stability. The results indicated that the catalysts is suitably developed as an efficient electrocatalysts for the preparation of syngas.

금속-유기 골격체 열분해를 통해 합성된 Co3O4/CoFe2O4 첨가 In2O3나노섬유를 이용한 고감도 고선택성 에탄올 센서

금속-유기 골격체 열분해를 통해 합성된 Co3O4/CoFe2O4 첨가 In2O3나노섬유를 이용한 고감도 고선택성 에탄올 센서

Oxygen Vacancy Engineering of MOF-Derived Zn-Doped Co3O4 Nanopolyhedrons for Enhanced Electrochemical Nitrogen Fixation.

Introducing oxygen vacancy (Vo) has been considered as an effective and significant method to accelerate the sluggish electrocatalytic nitrogen reduction reaction (NRR). In this work, a series of bimetallic zeolitic imidazolate frameworks based on ZIF-67 and ZIF-8 with varied ratios of Co/Zn have been applied as precursors to prepare Vo-rich Zn-doped Co3O4 nanopolyhedrons (Zn-Co3O4) by a low-temperature oxidation strategy. Zn-Co3O4 presents an ammonia yield of 22.71 μg h-1 mgcat.-1 with a high faradaic efficiency of 11.9% for NRR under ambient conditions. The remarkable catalytic performances are believed to result from the plentiful Vo as the Lewis acid sites and electron-rich Co sites to promote the adsorption and dissociation of N2 molecules. Remarkably, Zn-Co3O4 also demonstrates a high electrochemical stability. This work presents a guiding method for developing a stable and efficient electrocatalyst for the NRR.

Design of cobalt catalysed carbon nanotubes in bimetallic zeolitic imidazolate frameworks

Carbon nanotubes are the most effective way to enhance electrical conductivity between particles, although the growth mechanism in zeolitic imidazolate frameworks still remains elusive. According to our density functional theory calculations and experimental studies, the role of cobalt nanoparticles as catalysts was proved to induce graphitization during pyrolysis. In particular, the sizes and exposed facets of the Co particles play an important role in triggering a hierarchical carbon nanotubes. This work paves the way to control the growth of carbon nanotubes toward various applications.

Co-Nx bonds as bifunctional electrocatalytic sites to drive the reversible conversion of lithium polysulfides for long life lithium sulfur batteries

Lithium sulfur battery (LSB) is promising next-generation energy storage system due to its high theoretical energy density and low cost. However, the poor reaction reversibility weakened its application. Here, a bifunctional electrocatalyst with highly active Co-Nx sites was synthesized by pyrolyzing Co/Zn bimetallic zeolitic imidazolate frameworks and used as separator coating layer to improve the reversibility of LSB. Using zinc as sacrificial template, the severe agglomeration of cobalt is effectively avoided, and abundant Co-Nx active sites are obtained. Investigations in reaction kinetic reveal that Co-Nx sites have a bifunctional electrocatalytic activity towards Li2S deposition and dissolution during cycling. Density functional theory calculations further confirm the strong electrocatalytic effect of Co-Nx sites, which results in a reduced Gibbs free energy for the liquid-solid reactions of lithium polysulfides to Li2S. Under the same experimental condition, the introduction of Co-Nx bitunctional electrocatalyst contributed to a 31% reversible capacity increase for LSB, with a capacity of 896 mAh g−1 at 1 C, and a slow capacity decay rate of 0.033% per cycle over 1000 cycles. Even for thick electrode with a sulfur loading of 6 mg cm−2, a reversible capacity of 4.2 mAh cm−2 can still be obtained at 0.2 C over 100 cycles.

Double-shelled carbon nanocages grafted with carbon nanotubes embedding Co nanoparticles for enhanced hydrogen evolution electrocatalysis.

Herein, small Co nanoparticles (NPs) encapsulated in N-doped double-shelled carbon nanocages grafted with thin carbon nanotubes (Co@CNTs@DSCNCs) were synthesized from yolk-shell bimetallic zeolitic imidazolate framework (BMZIF). For HER electrocatalysis, they exhibit higher activity (η10 = 214 mV) and more favorable kinetics than Co@CNTs@PC (PC = porous carbon) with thick CNTs and large Co NPs derived from solid BMZIF cubes.

A mild approach to bimetallic ZIF-derived porous carbons as highly efficient oxygen reduction electrocatalysts

The bimetallic zeolitic imidazolate frameworks (BMZIFs) are excellent precursor electrochemical materials for energy storage and conversion technologies. In this paper, a series of BMZIFs catalysts based on ZIF-8 and ZIF-67 modified by a small amount of glucose were fabricated for Oxygen Reduction Reaction (ORR). With the reasonable glucose adding and further water as solvent, the modified BMZIFs (BM2-C6-50T) exhibits excellent ORR performance with the half-wave potential reaches of 0.84 V and the limiting current density of 5.26 mA cm−2, due to the large specific surface area of 387.18 m2 g−1 and the uniform micro/mesoporous structure. The glucose can significantly improve the graphitization degree and conductivity of the catalyst. Compared with the unmodified BMZIFs, the active material Co-Nx also gets more loading due to low-dimensional structures and increasing surface areas by the water solvent modification. This work can provide a green and mild approach to modify the structure of BMZIFs to effectively improve the electrocatalytic performance for derivatization catalysts.