Metal-based Metal-organic Frameworks Research Articles

Highly efficient N2 electroreduction to NH3 on Cu7·2S4/C with sulfur vacancies synthesized using a continuous microchannel reactor

The electrochemical nitrogen reduction reaction (NRR) has emerged as a sustainable and environmental–friendly alternative for ammonia synthesis compared with conventional Haber–Bosch process. However, considerable challenges persist in developing cost-effective catalysts for NRR. Herein, Cu7·2S4/C was synthesized using a continuous microchannel reactor followed by carbonization sulfurization at 600 °C. The as-prepared Cu7·2S4/C catalyst, featuring abundant sulfur vacancies, exhibited outstanding electrochemical performance for NRR, achieving an ammonia yield of 52 μg h−1mgcat.−1 and Faraday efficiency of 32.2%. In addition, density functional theory calculations suggest that sulfur vacancies contribute to a decrease in Gibbs free energy during N2-activated hydrogenation, thereby facilitating adsorption of N2 and formation of Cu–N bonds at catalytic active centers. This study introduces a novel strategy for synthesizing economical and efficient NRR electrocatalysts based on transition metal-based metal–organic frameworks.

Construction of bismuth based MOF for efficient removal of sodium diclofenac via adsorption and photocatalysis

The mass production and widespread use of Pharmaceuticals and Personal Care Products (PPCPs) have posed a serious threat to the water environment and public health. In this work, a green metal-based Metal Organic Framework (MOF) Bi-NH2-BDC was prepared and characterized, and the adsorption characteristics of Bi-NH2-BDC were investigated with typical PPCPs—diclofenac sodium (DCF). It was found that DCF mainly covered the adsorbent surface as a single molecular layer, the adsorption reaction was a spontaneous, entropy-increasing exothermic process and the adsorption mechanisms between Bi-NH2-BDC and DCF were hydrogen bonding, π-π interactions and electrostatic interactions. In addition, Bi-NH2-BDC also had considerable photocatalytic properties, and its application in adsorbent desorption treatment effectively solved the problem of secondary pollution, achieving a green and sustainable adsorption desorption cycle.

Revealing the Ambience-Dependent Structural Evolutions of Mo–Based Metal–Organic Frameworks with in Situ TEM for Efficient Electrocatalytic N2 Reduction to NH3

The electrocatalytic nitrogen reduction reaction (NRR) has been demonstrated to be the potential alternative strategy for NH3 production in the clean and sustainable manner. Various materials have been widely adopted for the NRR in recent years, and metal-based zeolite imidazole framework-8 (ZIF-8) and their derivatives have been extensively utilized. In this study, we used in situ TEM to probe the structural evolution of Mo-based zeolite imidazole framework-8 (Mo-ZIF-8) and provide the decomposition mechanism under various pyrolysis conditions [Figure 1a]. Upon pyrolyzing Mo-ZIF-8 under oxidative, inactive, and reductive environments, the ZIF-derived ZnO, Mo2C, and Mo nanoparticles (Mo-NPs) in porous N-doped carbon (PNC) are formed, respectively [Figure 1b]. At a lower concentration of Mo, Mo single atoms (Mo-SAs) were formed in the inactive environment, whereas Mo nanoclusters (Mo-NCs) were obtained under the reductive conditions [Figure 1b]. Furthermore, the Mo-related materials/PNC were served as the catalysts for the electrochemical NRR [Figure 1c]. Among all of the Mo-related materials, Mo-SA/PNC achieves a maximum NH3 yield rate [Figure 1d] and outstanding Faradic efficiency (FE) [Figure 1e] at -0.2 V ( vs. RHE), which is 1.4-fold and 8-fold higher than that of the Mo-NP/PNC, respectively. Our findings suggest some new guidelines for the rational design of the derivatives of metal-based metal–organic frameworks and their feasible application in various field. Figure 1

Simple activation effect on the EC hydrolysis performance of MOF structure

Transition metal-based metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) are considered as the ideal substitutes or supports for electrochemical catalysis field. However, due to the limited number of surface-active sites and the low conductivity of the bulk of MOFs/COFs, their electrocatalytic (EC) performance is usually promoted by the complicated multi-step decoration procedures. In this paper, a simple sequential-activation-step was verified to have the ability to improve considerably the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance of pristine Co-MOF (ZIF-67) material. For example, NC@Co from the carbonized and electrochemical activated ZIF-67 exhibited enhanced OER properties, while NC@CoxOy obtained via a sequential carbonize-oxidized-electrochemical activated procedure on ZIF-67 exhibited outstanding HER performance relatively. Density Functional Theory (DFT) calculations indicated that the in situ generated CoOOH was attributed to the improved HER/OER performance of the corresponding ZIF-67 activated derivatives with the redistribution of electron density, increased conductivity, and the optimized adsorption Gibbs free energy of hydrolysis intermediates. This work presents potential directions for the application of MOFs or COFs in the fields of electrochemical energy conversion through the electrochemical pathways.

Conductive Metal Organic Framework as Trapping Cathode Additive for High Performance Lithium-Sulfur Batteries

Lithium-Sulfur (Li-S) batteries with high capacity and energy density have arisen as one of the most promising secondary batteries. However, higher order lithium polysulfide (LiPSs) shuttling and insulating nature of sulfur cathode results in capacity degradation and premature failure of the cell [1]. Here for the first time, we have implemented conductive Cu metal-based Metal organic framework (Cu-MOF) as a Li-S battery cathode material. Cu-MOF cathode catalyst not only reduce the LiPSs shuttle effect but also increase the conductivity of Li-S battery cathode [2].Here, Cu-MOF pore morphology will trap the polysulfides and further prevent LiPSs shuttling. In addition, the well-defined architecture of organic ligands of Cu-MOF also participate to explicate the involved surface-binding mechanisms of S and polysulfide products. Furthermore, Cu-MOF improve the diffusion rate of Li ions, shackling LiPSs, upsurging conduction of electrons/ions, and regulating the deposition of Li2S2/Li2S towards cathode side [3]. Furthermore, sulfur active material is well percolated inside the pores of conductive Cu-MOF which shows the long-cycling performance as shown in Figure 1.Benefiting from the unique fibrous, porous, interwoven structure, the conductive MOF@S-composite cathode demonstrates a high initial capacity of 1671 mAh g–1 at 0.05 C rate with a good coulombic efficiency of >95% and the outstanding capacity of 849 mAh g-1 cycles even after 200 cycles at the 0.5 C-rate with coulombic efficiency of 98.3%. It is believed that, the experimental findings and mechanistic understanding of Cu-MOF cathode in this work will open a new avenue for the further development of other conductive MOFs in the Li-S batteries. Figure 1: Cycling performance of S@Cu-MOF composite at 0.5 C-rate. References Mingyue Wang, Zhongchao Bai, Ting Yang, Chuanhao Nie, Xun Xu, Yunxiao Wang, Jian Yang, Shixue Dou, and Nana Wan."Advances in High Sulfur Loading Cathodes for Practical Lithium-Sulfur Batteries." Energy Mater, no.12 (2022): 2201585.Dan Luo, Chaojie Li, Yongguang Zhang, Qianyi Ma, Chuyin Ma, Yihang Nie, Matthew Li, Xuefei Weng, Rong Huang, Yan Zhao, Lingling Shui, Xin Wang, Zhongwei Chen. "Design of Quasi-MOF Nanospheres as a Dynamic Electrocatalyst toward Accelerated Sulfur Reduction Reaction for High-Performance Lithium–Sulfur Batteries." Mater, no.34 (2022): 210554. Jun Zhang, Ye Shi, Yu Ding, Lele Peng, Wenkui Zhang, Guihua Yu. "A Conductive Molecular Framework Derived Li2S/N,P-Codoped Carbon Cathode for Advanced Lithium–Sulfur Batteries." Energy Mater, no.7 (2017): 1602876. Figure 1

Environment-Dependent Structural Evolution and Electrocatalytic Performance in N2 Reduction of Mo-Based ZIF-8

In this study, we used in situ transmission electron microscopy to probe the structural evolution of Mo-based zeolite imidazole framework-8 (Mo-ZIF-8) under various gaseous environments. Upon pyrolyzing Mo-ZIF-8 under oxidative, inactive, and reductive environments, the formation of Mo-related materials, including Mo2C, Mo nanoparticles, Mo nanoclusters, and Mo single atoms (Mo-SAs), is well-controlled to be anchored on the porous N-doped carbon (PNC), and the evolution mechanisms are clearly provided. Furthermore, we discussed the performance of the Mo-related materials/PNC for the electrochemical nitrogen reduction reaction (NRR). Mo-SA/PNC achieves a maximum NH3 yield rate of 15.34 μg h–1 mg–1 and a Faradic efficiency of 24.03% for NRR at a potential of −0.2 V versus reversible hydrogen electrode. Our findings suggest guidelines for the rational design of the derivatives of metal-based metal–organic frameworks and their feasible application.

Efficient removal and sensing of copper(II) ions by alkaline earth metal-based metal–organic frameworks

A class of alkaline earth metal-based metal–organic frameworks (MOFs), namely NDCMOF(Ca) and NDCMOF(Sr), has been synthesized using 2,6-naphthalenedicarboxylic acid (NDC) as the linker. In view of the biocompatibility of the starting materials, these MOFs are expected to be environmentally benign and, in this work, have been employed for the removal of copper(II) ions (Cu2+) from aqueous systems. The results showed that the maximum adsorption capacities of NDCMOF(Ca) and NDCMOF(Sr) for Cu2+ were 299.4 and 398.4 ​mg ​g−1, respectively, which were comparable to those of related MOFs and porous materials. Meanwhile, NDCMOF(Ca) and NDCMOF(Sr) displayed blue luminescence in the solid state at room temperature upon photoexcitation with ultraviolet (UV) light. This emission would be readily quenched after the adsorption of Cu2+ ions. Such visible changes in the observed color and emission of the MOFs have rendered them versatile adsorbents and sensors for Cu2+ in the aqueous environment.

Mixed-Valent Stellated Cuboctahedral Cu(2,4-Imdb)-MOF for Trace Water Detection.

Developing an economical and robust sensor using an earth-abundant metal-based metal-organic framework (MOF) to detect trace water content rapidly is crucial for laboratories and chemical industries. Herein, a mixed-valent chiral [{Cu+Cu32+(2,4-Imdb)3(H2O)3}·Cl]∞ MOF manifests atypical quantitative detection of a trace amount of water [0.016% (v/v)] in organic solvents. Single-crystal X-ray diffraction and time-correlated single-photon counting supported the mechanism for turn-on fluorescence.

A reusable MOF supported single-site nickel-catalyzed direct N-alkylation of anilines with alcohols

The direct N-alkylation of amines with alcohols is an efficient route through a borrowing hydrogen (BH) strategy. Herein, a highly selective, and reusable Ni(II)-bipyridine-based metal-organic framework (MOF) catalyst was designed for this organic transformation. This earth-abundant metal-based metal-organic framework (MOF) catalyst significantly outperform their homogeneous analogues and the immobilized catalyst was reusable for at least up to 4 cycles without significant decrease in the yield of the target product.

Effect of Coordinated Solvent Molecules in Cu-MOF on Enzyme Free Sensing of Glucose and Lactate in Physiological pH

Developing a nonenzymatic sweat sensor for selective determination of glucose and lactate holds great significance in clinical diagnostics. Among various catalysts, transition metal-based metal-organic frameworks (MOF) have recently drawn more attention due to their tunable porosity and enhanced electrocatalytic activity. The presence of the solvent molecule in the framework can influence both structural and electrochemical properties. In the present work, Copper-terephthalate (CuBDC) MOF was synthesized in a solvothermal method with different time durations. The effect of the coordinated solvent molecules on the metal centre on structural and electrocatalytic properties was systematically investigated using various characterization techniques. As most of the copper-based composites reported so far showed performance in an alkaline medium, we demonstrate the detection of glucose and lactate in a neutral medium that enables direct analyte measurement from the body fluid. Electrochemical studies indicate that the solvated structure shows superior sensitivity to the desolvated MOF for glucose and lactate. The high sensitivity of the solvated MOF is attributed to the favourable solvent exchange mechanism and ion diffusion through the channels of the MOF. Furthermore, CuBDC12E and CuBDC48E show negligible interference toward competing analytes. The proposed sensor also exhibits good sensing performance in artificial sweat, making it suitable for a non-invasive, practical sweat sensor.

Self-assembly of 3p-Block Metal-based Metal-Organic Frameworks from Structural Perspective

Self-assembly of 3p-Block Metal-based Metal-Organic Frameworks from Structural Perspective

Research Progress of Oxygen Evolution Reaction Catalysts for Electrochemical Water Splitting

The development of a low-cost and high-efficiency oxygen evolution reaction (OER) catalyst is essential to meet the future industrial demand for hydrogen production by electrochemical water splitting. Given the limited reserves of noble metals and many competitive applications in environmental protection, new energy, and chemical industries, many studies have focused on exploring new and efficient non-noble metal catalytic systems, improving the understanding of the OER mechanism of non-noble metal surfaces, and designing electrocatalysts with higher activity than traditional noble metals. This Review summarizes the research progress of anode OER catalysts for hydrogen production by electrochemical water splitting in recent years, for noble metal and non-noble metal catalysts, where non-noble metal catalysts are highlighted. The categories are as follows: (1) Transition metal-based compounds, including transition metal-based oxides, transition metal-based layered hydroxides, and transition metal-based sulfides, phosphides, selenides, borides, carbides, and nitrides. Transition metal-based oxides can also be divided into perovskite, spinel, amorphous, rock-salt-type, and lithium oxides according to their different structures. (2) Carbonaceous materials and their composite materials with transition metals. (3) Transition metal-based metal-organic frameworks and their derivatives. Finally, the challenges and future development of the OER process of water splitting are discussed.

Group 4 Metal-Based Metal—Organic Frameworks for Chemical Sensors

Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 metal-based (e.g., zirconium, titanium, hafnium, and cerium) MOFs, have become especially of interest for the sensors requiring the operations in aqueous media owing to their remarkable chemical stability in water. Research efforts have been made to utilize these group 4 metal-based MOFs in chemosensors such as luminescent sensors, colorimetric sensors, electrochemical sensors, and resistive sensors for a range of analytes since 2013. Though several studies in this subfield have been published especially over the past 3–5 years, some challenges and concerns are still there and sometimes they might be overlooked. In this review, we aim to highlight the recent progress in the use of group 4 metal-based MOFs in chemical sensors, and focus on the challenges, potential concerns, and opportunities in future studies regarding the developments of such chemically robust MOFs for sensing applications.

Construct efficient substrate transport and catalytic sub-nanochannels in metal-organic framework-based nanozymes for boosting peroxidase-like catalytic activity

Transition metal-based metal-organic frameworks (MOFs) nanozymes, as an ideal artificial metalloenzymes, have recently attracted extensive attention due to their unique porous structure and promising applications in many fields. However, due to the lack of in-depth understanding of the catalytic mechanisms of MOF-based nanozymes, especially the influence of the inherent structure of MOFs on the enzyme-like catalytic process, it is still a very difficult task to reasonably construct high-performance MOF-based nanozymes to date. Inspired by biological ion channels with ultra-high ion conductivity and selectivity, a facile metal node engineering strategy was developed in this study to directly construct highly efficient 1D substrate transport and catalytic sub-nanochannels within Fe-based (MIL-53(Fe)) nanozymes. Through Ni-doping and H2-treatment at low temperature (200 °C), NiII and mixed-valence FeII/FeIII nodes were successfully generated in 1D iron oxide octahedral chains of MIL-53(Fe) to act as adsorption and reversible catalytic sites of H2O2, respectively. Benefiting from the confinement effect and optimized catalytic microenvironment of NiII and FeII decorated sub-nanochannels, the as-obtained NixFe-MOF-based nanozymes exhibited lower values of Km (0.068 mM) toward H2O2 and larger νmax (2.92 × 10−7 M s−1) in comparison with previously reported studies. Furthermore, the well-designed nanozymes illustrated high sensitivity and selectivity toward the detection of H2O2 and glutathione. This work not only deepens our understanding of enzyme-mimetic activity of MOF, but also the proposed strategy could be potential used for the design and synthesis of other highly efficient MOF-based catalysts.

Nonbonded Zr4+ and Hf4+ Models for Simulations of Condensed Phase Metal–Organic Frameworks

Recently, the practical applications of tetravalent metal-based metal–organic frameworks (MOFs) have been drawing increasing attention due to their excellent stability and varied functionality. Understanding the behavior of MOFs at the atomic level is important for their rational design and postsynthetic optimization. In classical simulations, the cationic dummy atom model, where the charge of the metal ion is distributed to surrounding dummy particles, has shown robustness in providing the appropriate coordination geometry while retaining the flexibility in the metal ligand interaction. Here, we present a set of eight-coordinated tetravalent metal (Zr4+, Hf4+) dummy model force fields with 12-6-4 type Lennard–Jones potential for describing ion-induced dipole interactions. This model can reproduce both the experimental solvation free energy of the bare ion and good metal–ligand distances and has been validated as useful and transferable among MOFs with the same metal-core topology. The model is inherently modular since nodes and linkers are independently parametrized. It was tested with three different solvents which all led to stable structures. It also was been further validated with different metal node structures and different linkers, Zr/Hf mixed MOFs, and defects containing MOFs. Since the model is nonbonded, the process of metal–ligand substitutions could be studied. The flexibility of the model makes its applicability to chemical problems broad.

Transition metal-based metal–organic frameworks for environmental applications: a review

Rapid industrialization is deteriorating air and water quality by exposing life to a wide range of pollutants, thus calling for efficient and affordable remediation strategies. Metal–organic frameworks (MOFs) are emerging materials for environmental remediation applications due to their high surface area, ordered porous structure, and application-specific tailoring of properties. In particular, transition metal-based frameworks are advanced adsorbents and catalysts for the remediation of organic and gaseous pollutants. Physicochemical properties are mainly dependent on the choice of the metal center, the oxidation state, and organic linkers. Bimetallic-, polyoxometalate-, and metal oxide-incorporated frameworks find applications as photocatalysts for decontamination of dyes, phenolic compounds, pesticides and pharmaceutical drugs under ultraviolet (UV)/visible radiations. Large surface area coupled with high activity of transition metal frameworks allows the capture and removal of inorganic and volatile organic pollutants. Transition metal frameworks convert gaseous pollutants into value-added chemicals. Frameworks containing synthetic and natural fibers are currently studied to remove chemical warfare agents.

Modulating Charge Transfer Efficiency of Hematite Photoanode with Hybrid Dual-Metal-Organic Frameworks for Boosting Photoelectrochemical Water Oxidation.

The glorious charge transfer efficiency of photoanode is an important factor for efficient photoelectrochemical (PEC) water oxidation. However, it is often limited by slow kinetics of oxygen evolution reaction. Herein, a dual transition metal‐based metal–organic frameworks (MOF) cocatalyst, Fe@Ni–MOF, is introduced into a titanium‐doped hematite (Fe2O3:Ti) photoanode. The combination of Ni and Fe can optimize the filling of 3d orbitals. Moreover, the introduction of Fe donates electrons to Ni in the MOF structure, thus, suppressing the irreversible (long‐life‐time) oxidation of Ni2+ into Ni3+. The resulting Fe@Ni–MOF/Fe2O3:Ti photoanode exhibits ∼threefold enhancement in the photocurrent density at 1.23 V versus the reversible hydrogen electrode. Kinetic analysis of the PEC water oxidation processes indicates that this performance improvement is primarily due to modulating the charge transfer efficiency of hematite photoanode. Further results show that a single transition metal‐based MOF cocatalyst, Ni–MOF, exhibits slow charge transfer in spite of a reduction in surface charge recombination, resulting in a smaller charge transfer efficiency. These findings provide new insights for the development of photoelectrodes decorated with MOFs.

Bimetallic Metal-Organic Framework-Derived Nanosheet-Assembled Nanoflower Electrocatalysts for Efficient Oxygen Evolution Reaction.

Non-noble metal-based metal-organic framework (MOF)-derived electrocatalysts have recently attracted great interest in the oxygen evolution reaction (OER). Here we report a facile synthesis of nickel-based bimetallic electrocatalysts derived from 2D nanosheet-assembled nanoflower-like MOFs. The optimized morphologies and large Brunauer-Emmett-Teller (BET) surface area endow FeNi@CNF with efficient OER performance, where the aligned nanosheets can expose abundant active sites and benefit electron transfer. The complex nanoflower morphologies together with the synergistic effects between two metals attributed to the OER activity of the Ni-based bimetallic catalysts. The optimized FeNi@CNF afforded an overpotential of 356 mV at a current density of 10 mA cm-2 with a Tafel slope of 62.6 mV dec-1 , and also exhibited superior durability with only slightly degradation after 24 hours of continuous operation. The results may inspire the use of complex nanosheet-assembled nanostructures to explore highly active catalysts for various applications.

Enhanced Low-Frequency Electromagnetic Properties of MOF-Derived Cobalt through Interface Design.

It is still a formidable challenge to ameliorate the low-frequency electromagnetic property of conventional microwave-absorbing materials, which may be conquered by the coexistence of both strong dielectric and magnetic loss ability in low-frequency range and the perfect balance between complex permittivity and permeability with the help of structural design. Herein, by virtue of appropriate composition and structure of Co3[HCOO]6·dimethylformamide parallelepipeds, one-dimensional spongelike metallic Co can be directly synthesized for the first time with strong magnetic loss in the low-frequency range. Furthermore, attenuation ability and impedance matching condition have been improved through the construction of interfacial structures between inner cobalt and surface carbon. With the structure of carbon changed from fragments to vertically aligned nanoflakes and eventually to a thick layer with extra fragments, the dielectric loss would be continuously strengthened, while the magnetic loss maintains well, followed by a remarkable decline. A perfect balance between dielectric and magnetic loss has been achieved by sample S-Co/C-0.3 with minimum reflection loss value around -20 dB and effective absorption frequency range about 3.84 GHz in the C band. Excellent microwave absorption performance can also be realized in X and Ku bands. In addition, as-prepared Co and Co/C composites can also be potentially applied in electromagnetic shielding. The findings may pave the way for the manufacture of metal-based metal-organic framework derivatives and the design of lightweight low-frequency electromagnetic materials.

Stable Metal-Organic Frameworks with Group 4 Metals: Current Status and Trends.

Group 4 metal-based metal–organic frameworks (MIV-MOFs), including Ti-, Zr-, and Hf-based MOFs, are one of the most attractive classes of MOF materials owing to their superior chemical stability and structural tunability. Despite being a relatively new field, MIV-MOFs have attracted significant research attention in the past few years, leading to exciting advances in syntheses and applications. In this outlook, we start with a brief overview of the history and current status of MIV-MOFs, emphasizing the challenges encountered in their syntheses. The unique properties of MIV-MOFs are discussed, including their high chemical stability and strong tolerance toward defects. Particular emphasis is placed on defect engineering in Zr-MOFs which offers additional routes to tailor their functions. Photocatalysis of MIV-MOF is introduced as a representative example of their emerging applications. Finally, we conclude with the perspective of new opportunities in synthesis and defect engineering.