Bimetallic Metal-organic Frameworks Research Articles

Interpretable Data-Driven Descriptors for Establishing the Structure-Activity Relationship of Metal-Organic Frameworks Toward Oxygen Evolution Reaction.

The development of readily accessible and interpretable descriptors is pivotal yet challenging in the rational design of metal-organic framework (MOF) catalysts. This study presents a straightforward and physically interpretable activity descriptor for the oxygen evolution reaction (OER), derived from a dataset of bimetallic Ni-based MOFs. Through an artificial-intelligence (AI) data-mining subgroup discovery (SGD) approach, a combination of the d-band center and number of missing electrons in eg states of Ni, as well as the first ionization energy and number of electrons in eg states of the substituents, is revealed as a gene of a superior OER catalyst. The found descriptor, obtained from the AI analysis of a dataset of MOFs containing 3-5d transition metals and 13 organic linkers, has been demonstrated to facilitate in-depth understanding of structure-activity relationship at the molecular orbital level. The descriptor is validated experimentally for 11 Ni-based MOFs. Combining SGD with physical insights and experimental verification, our work offers a highly efficient approach for screening MOF-based OER catalysts, simultaneously providing comprehensive understanding of the catalytic mechanism.

Bimetallic MOF‐Based Fibrous Device for Noninvasive Bilirubin Sensing

AbstractNoninvasive and real‐time detection of bilirubin concentration enables rapid assessment of liver health status and the diagnosis of jaundice‐related diseases. Herein, the study proposes a strategy to uniformly grow bimetallic FeCo metal–organic framework (MOF) films onto the surface of carbonized electrospun nanofibers via a stepwise growth strategy involving an induction effect of oxide nanomembrane prepared by atomic layer deposition, to realize high‐performance flexible nanofiber bilirubin sensors. Compared with monometallic MOF, the FeCo bimetallic MOF can attain a larger specific surface area, thus augmenting the exposed active sites. Furthermore, the synergistic interaction between the bimetallic active sites on the MOF film and the carbonized nanofibers enhances the electronic conduction network, thereby significantly enhancing the catalytic activity of the flexible electrode for bilirubin. The current nanofibers sensor exhibits excellent performance in bilirubin detection, in terms of high sensitivity, large linear detection range, and low detection limit. The synthesis of bimetallic MOF films on flexible fibers holds promise for the development of highly sensitive electrodes for wearable bilirubin detection devices.

In Situ Phosphorization for Constructing Ni5P2-Ni Heterostructure Derived from Bimetallic MOF for Li-S Batteries.

Heterostructured materials commonly consist of bifunctions due to the different ingredients. For host material in the sulfur cathode of lithium-sulfur (Li-S) batteries, the chemical adsorption and catalytic activity for lithium polysulfides (LiPS) are important. This work obtains a Ni5P2-Ni nanoparticle (Ni5P2-NiNPs) heterostructure through a confined self-reduction method followed by an in situ phosphorization process using Al/Ni-MOF as precursors. The Ni5P2-Ni heterostructure not only has strong chemical adsorption, but also can effectively catalyze LiPS conversion. Furthermore, the synthetic route can keep Ni5P2-NiNPs inside of the nanocomposites, which have structural stability, high conductivity, and efficient adsorption/catalysis in LiPS conversion. These advantages make the assembled Li-S battery deliver a reversible specific capacity of 619.7 mAhg- 1 at 0.5C after 200 cycles. The in situ ultraviolet-visible technique proves the catalytic effect of Ni5P2-Ni heterostructure on LiPS conversion during the discharge process.

Bimetallic MOFs derivative LaFeO3@C for efficient and stable carbon-based perovskite solar cells

Carbon-based MAPbI3 perovskite solar cells (C-PSCs) have attracted significant attention due to their low cost and stable performance. However, due to inherent structural defects and an energy level mismatch between the perovskite layer and the carbon electrode, C-PSCs still show a poorer power conversion efficiency (PCE) than traditional perovskite solar cells (PSCs). In this study, LaFeO3@C nanocomposite particles were successfully synthesized via pyrolysis of La-containing MIL-100(Fe) MOF gel. By introducing these pre-synthesized LaFeO3@C bimetallic composite oxide nanoparticles into the carbon electrode, the device featuring a FTO/SnO2/CH3NH3PbI3/LaFeO3@C/C architecture achieved an impressive maximum PCE of 16.35%, surpassing that of the pristine device by 9.36%. The enhanced optoelectronic performance can be primarily attributed to enhanced interfacial contacts, superior interfacial charge extraction ability, and better electrical conductivity. The LaFeO3@C-based device maintained more than 90% of the initial PCE after being stored for 31 days at room temperature and ambient humidity. This study provides a novel strategy for the preparation of efficient and stable C-PSCs from the perspective of spatial structure regulation of bimetallic MOF-based composites.

Electrospun nanofiber composite based on bimetallic metal–organic framework/halloysite nanotubes/deep eutectic solvents/molecularly imprinted polymers for thin film microextraction of sulfonamides in milk, eggs and chicken meat by HPLC analysis

Herein, electrospun nanofibers based on bimetallic metal–organic framework@ functionalized halloysite/deep eutectic solvents/molecularly imprinted polymers was synthesized as new solid phase extractant for thin film microextraction of sulfacetamide, sulfamethoxazole, sulfamethazine and silversulfadiazine by HPLC-UV analysis. After synthesizing new phase through electrospinning nanofibers and thin film fabrication, we effectively leverage the synergistic properties of these materials within the composite structure. The resultant thin film nanocomposite, which integrates molecularly imprinted nanofibers, highlights the presence of inorganic nanotubes called halloysite, functionalized with a deep eutectic solvent and bimetallic metal–organic frameworks. Characterization of synthesized thin films were successfully characterized for structural, morphological, and surface analysis using infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). In this study, a syringe design was employed for the microextraction of sulfonamides (SAs) using thin film microextraction, which is carried out in two stages: adsorption and desorption, both within the syringe. The effects of several experimental conditions on desorption stage, including desorption parameters including pH, desorption solvent type, and ultrasonication time were studied by the single factor at a time. A Box-Behnken design (BBD) was applied to optimize the significant variables to obtain the optimum extraction conditions. The detection limit of the method was 0.003 µg/L and also the limit of quantification method was in the range of 0.01 µg/L. These results demonstrate the presented thin film microextraction method can serve as a good candidate for the microextraction and determination of sulfonamides in food samples like milk, eggs and chicken meat.

Petal-by-petal tree-blossoming shaped bimetallic MOF-based material over SBA-15: Diverse designability, synergistic catalysis, and thermodynamics/kinetic analysis

Transition metal-based bimetallic MOF (CoMo-ZIF) with two different metal ions (Co/Mo) possess specific synergistic catalytic effect in olefins oxidation, but poor diffusion efficiency and less active areas limit its application. Herein, a novel CoMo-ZIF-based nanocomposite is fabricated via an in-situ solvothermal approach to break down active area or diffusion efficiency barrier of CoMo-ZIF via employing SBA-15 as the matrix and nanosacle polyoxometalate (POM) as external active species. Characterizations reveal that pristine rose-type CoMo-ZIF (∼350 nm diameter) alters to rambutan-like hollow sphere and eventually self-assembles into hierarchical petal-by-petal nanoflakes (ca. 20∼50 nm in thickness) after SBA-15 and POM introduction, respectively. POM@CoMo-ZIF@SBA-15 with super large pore size (10.44 nm) and increased active (Co2+ + Co3+)/satellite (1.92) exhibits excellent catalytic activity in cyclopentene (CPE) oxidation to glutaric acid (GAC) with 57.1 % CCPE, 61.6 % SGAC, and good reusability with 54.3∼57.1 % CCPE and 58.4∼63.2 % SGAC during 6 cycles. What's more, thermodynamic analysis indicates that CPE oxidation to GAC is a spontaneous reaction at 273.15∼373.15 K, and kinetic study shows that the key to develop CPE to GAC is to reduce activation energies of cyclopentene oxide ring-opening to 1,2-cyclopentanediol (73.8298 kJ⋅mol−1) and glutaradehyde (118.4571 kJ⋅mol−1). This study not only pioneers a promising strategy for oriented design of MOF-based materials, but also serves as a valuable reference for the computation of various chemical reactions.

A novel mercapto-functionalized bimetallic Zn/Ni-MOF adsorbents for efficient removal of Hg(II) in wastewater

Heavy metals, especially mercury ions, pose extreme hazards to human health and environmental sustainability. Receiving significant interest lately, metal-organic frameworks with mercapto-functionalization (SH-MOFs) have shown impressive efficacy in effectively eliminating highly hazardous Hg(II) from wastewater. In this investigation, a novel mercapto-functionalized Zn/Ni bimetallic MOF (ZNM-2) was synthesized utilizing a simple solvothermal technique employing zinc and nickel as metal sources and 2-mercaptobenzimidazole (MBI) as the organic ligand. The Hg(II) adsorption capacity by ZNM-2 reached 744.4 mg/g, surpassing that of a single-nickel MOF (NM) 328.8 mg/g. More impressively, ZNM-2 successfully eliminated 99.99 % of Hg(II) from actual water samples, achieving a concentration level for Hg(II) that is lower than the threshold of 1.0 μg/L specified in the GB 5749–2022 drinking water standard. When the pH of Hg(II) solution ranged from 2.0 to 6.0, it exhibited exceptional adsorption capacity and sustained high removal efficiency throughout four consecutive regeneration cycles. The adsorption mechanisms observed in this study were found to conformity with the Langmuir model and PSO kinetic model, suggesting that the predominant mode of Hg(II) adsorption is through a chemisorption process occurring at a monolayer level. The superior Hg(II) removal rate of ZNM-2 can be attributed to the predominant coordination of Hg(II) to the thiol (-SH) groups, as revealed by a combination of FT-IR, XPS analysis, and DFT calculations. Therefore, ZNM-2 is an efficacious Hg(II) absorbent that provides a novel approach to alleviate mercury contamination in wastewater.

Symbiotic defect-reinforced bimetallic MOF-derived fiber components for solar-assisted atmospheric water collection

Conversion of atmospheric water to sustainable and clean freshwater resources through MOF-based adsorbent has great potential for the renewable environmental industry. However, its daily water production is hampered by susceptibility to agglomeration, slow water evaporation efficiency, and limited water-harvesting capacity. Herein, a solar-assisted bimetallic MOF (BMOF)-derived fiber component that surmounts these limitations and exhibits both optimized water-collect capacity and short adsorption-desorption period is proposed. The proposed strategy involves utilizing bottom-up interface-induced assembly between carboxylated multi-walled carbon nanotube and hygroscopic BMOF on a multi-ply glass fiber support. The designed BMOF (MIL-100(Fe,Al)-3) skeleton constructed using bimetallic-node defect engineering exhibits a high specific surface area (1,535.28 m2/g) and pore volume (0.76 cm3/g), thereby surpassing the parent MOFs and other reported MOFs in capturing moisture. Benefiting from the hierarchical structure of fiber rods and the solar-driven self-heating interface of photothermal layer, the customized BMOF crystals realize efficient loading and optimized water adsorption-desorption kinetics. As a result, the resultant fiber components achieve six adsorption-desorption cycles per day and an impressive water collection of 1.45 g/g/day under medium-high humidity outdoor conditions. Therefore, this work will provide new ideas for optimizing the daily yield of atmospheric water harvesting techniques.

Toward Developing Superior Cu-Based Metal-Organic Framework-Derived Materials for Electrocatalytic Oxidation of Ethanol.

This project addresses the urgent need for efficient and cost-effective development of electrocatalysts for the ethanol oxidation reaction (EOR). This reaction offers promising renewable energy solutions but faces challenges due to the slow EOR kinetics, typically requiring costly noble metal catalysts. To overcome these limitations, this study focuses on developing CuZn-based EOR catalysts derived from metal-organic frameworks (MOFs), focusing on understanding the structure-performance relationship between pristine MOF-based electrocatalysts and their pyrolyzed counterparts. Herein, bimetallic MOF materials with varying Cu/Zn ratios were synthesized, followed by pyrolysis to produce carbonized counterparts while preserving the fundamental structure but with altered physicochemical properties. Comparative EOR studies revealed the superior performance of pyrolyzed MOFs, demonstrating that optimized Zn-loading is crucial over Cu-based framework for catalyst performance and durability. Overall, this work highlights the potential of MOF-derived Cu-based catalysts for renewable energy applications and provides insights into optimizing their performance through controlled synthesis and post-treatment strategies.

Inducing energy storage: Bimetallic MOF-derived Co3O4/NiO nanocomposites for advanced electrochemical applications

Multimetallic-based nanocomposites have arisen as highly capable functional materials, offering new horizons for applications in electrochemical energy storage. Among the platforms for synthesizing a diverse range of nanostructures incorporating metals, oxides, sulfides, and nitrides within a porous carbon matrix, metal–organic frameworks (MOFs) stand out as exceptional candidates. In this study, we successfully synthesized Co3O4/NiO nanocomposites from a Co/Ni MOF, employing a 2-mthylimidazole (2 MI) linker as a key component in the synthesis process. The resulting nanocomposites reveal a notable synergy of characteristics, including high crystallinity, retained morphologies, and adjustable textural features, all of which are validated through a comprehensive series of characterization analyses. Leveraging these distinct advantages, the primary objective of this research is to fabricate Co3O4/NiO nanocomposites derived from a bimetallic MOF, with a keen focus on harnessing their potential for electrochemical energy storage uses. Electrochemical analysis of the Co3O4/NiO nanocomposite reveals an exceptional capacitance of up to 180.4F/g at 0.2 A/g, demonstrating exceptional performance and robust stability over a notable 1200 cycles. Furthermore, the Co3O4/NiO nanocomposite exhibits remarkable electrocatalytic performance, achieving a utmost current density of 135.6 mA/cm2 at 0.6 V along with excellent long-term electrochemical stability. This remarkable capacitance and oxidation of methanol underscores the suitability of these nanocomposites for advanced electrochemical energy storage and fuel cell uses, emphasizing their potential for enriched performance in such systems.

Non-enzymatic electrochemical sensor based on ionic liquid [BMIM][PF6] functionalized zirconium‑copper bimetallic MOF composite for the detection of nitrite in food samples

In this study, we developed an electrochemical sensor utilizing a composite material consisting of zirconium‑copper bimetallic metal-organic framework functionalized with ionic liquid [BMIM][PF6]. This composite material was fabricated by simple wet impregnation method, which not only maintains excellent electrocatalytic activity but also enhances electron transfer rate and electroactive surface area. The ZrCu-MOF-818/ILs composite modified electrode has been demonstrated as an effective tool for the detection of nitrite. The electrode exhibited a remarkable limit of detection (LOD) of 0.148 μM and wide linear ranges of 6–3000 μM and 3000–5030 μM. It is worth noting that the sensor displayed excellent reproducibility and repeatability, with relative standard deviation (RSD) values of 1.06% and 1.37%, respectively. Furthermore, the proposed method was successfully applied for the detection of nitrite in tap water and pickle juice.

Synthesis of Zr/La-BTC Bimetallic Metal-Organic Framework (MOF) for Oleic Acid Esterification

Biodiesel plays an essential role in renewable energy as an alternative fuel to tackle the challenges of global warming, environmental degradation, and alternative fossil fuels. Oleic acid can be converted into biodiesel by the esterification process, which employs heterogeneous catalysts such as metal-organic frameworks (MOF). In this study, Zr/La-BTC MOFs were used as different kinds of catalysts to change oleic acid into biodiesel. The characterization results of Zr-BTC, La-BTC, and Zr/La-BTC using FTIR and XRD show that the MOF has been successfully formed. The crystallite sizes for La-BTC, and Zr/La-BTC MOFs are 15.7407 nm and 39.0392 nm, respectively. The surface area of Zr-BTC, La-BTC, and Zr/La-BTC MOFs are 167.101 m2/g, 12.328 m2/g, and 4.764 m2/g. The morphology of Zr-BTC MOF using SEM is irregular, La-BTC is rod-shaped crystal, and Zr/La-BTC is like a knot bond with a narrow waist. The most optimal reaction was obtained at a 5% (w/w) catalyst dosage of total oleic acid and methanol (1:60 mol), 65 °C, and a reaction time of 4 hours, producing 78.11% oleic acid conversion. GC-MS analysis identified that the biodiesel contains oleic acid, palmitic acid, methyl oleate, and methyl palmitate.

Metal‐organic frameworks‐assisted electrochemical sensing toward magnesium in medicinal and edible homologous for pharmacological evaluation.

AbstractGiven the importance of Magnesium (Mg) assay for efficacy evaluation of medicinal and edible homologous (MEH), an electrochemical sensor is designed by exploiting the cooperative properties of metal–organic frameworks (MOFs) and gold nanoparticles (AuNPs). To be specific, the constructed bimetallic MOFs ((FeZr)MOF) are designed by using Zr(IV) and Fe(III) clusters as metal sources, which provide a large platform for AuNPs attachment to design signal probes. Benefitting from the catalytic properties of (FeZr)MOF toward hydroxylamine, electrochemical signal is attained for Mg2+ analysis with the detection limit to be 3 μM (corresponding to 0.072 μg g−1). Relying on DNAzymes as recognition elements, good anti‐jamming is achieved for Mg2+ analysis against the coexisting ions in Puerarin, Chinese wolfberry, hawthorn and dangshen. With the superiority of rapid response, acceptable sensitivity and specificity, the electrochemical sensor provides a useful pattern for assessing the pharmacological effects of MEH substances, pointing to reasonable selection and combination of multiple health function dietary therapy formulas.

Tailoring the Electrochemical Responses of MOF-74 Via Dual-Defect Engineering for Superior Energy Storage.

Rationally designed defects in a crystal can confer unique properties. This study showcases a novel dual-defects engineering strategy to tailor the electrochemical response of metal-organic framework (MOF) materials used for electrochemical energy storage. Salicylic acid (SA) is identified as an effective modulator to control MOF-74 growth and induce structural defects, and cobalt cation doping is adopted for introducing a second type of defect. The resulting dual-defects engineered bimetallic MOF exhibits a discharging capacity of 218.6 mAh g-1, 4.4 times that of the pristine MOF-74, and significantly improved cycling stability. Moreover, the engineered MOF-74(Ni0.675Co0.325)-8//Zn aqueous battery shows top energy/power density performances for Ni-Zn batteries (266.5Wh kg-1, 17.22kW kg-1). Comprehensive investigations reveal that engineered defects modify the local coordination environment and promote the in situ electrochemical reconfiguration during operation to significantly boost the electrochemical activity. This work suggests that rational tailoring of the defects within the MOF crystal is an effective strategy to manipulate the coordination environment of the metal centers and the corresponding electrochemical reconfiguration for electrochemical applications.

Construction of rose-type Co/Mo bimetal MOF and MOF-derived W embedded composites: Structure, reactivity, and dynamic simulation

Transition metal organic framework-derived materials are potential catalysts for cycloolefins oxidation, and it is essential to develop them with sufficient intrinsic activity and more efficient structure. Herein, we designed Co/Mo bimetallic MOF with rose-type structure as a support for synthesizing CoMo-ZIF@IL/W catalyst with lamelliform structure and abundant Co, Mo, and W active sites for cyclopentene tandem oxidation to glutaraldehyde. Characterization results reveal that: 1) Mo implantation dramatically increases pore size (2.15 → 28.91 nm) of monometallic MOF Co-ZIF; 2) IL introduction significantly improves active (Co2+ + Co3+) / satellite content ratio from 1.85 to 2.5; 3) MOF morphology can be completely changed through post-synthetic modification via IL, rather than just during the synthesis process. Meanwhile, CoMo-ZIF@IL/W exhibits high activity and excellent reuse properties in cyclopentene oxidation. Remarkably, dynamic simulation supported via detailed kinetic parameters (pre-exponential factors A1–3 = 1.17 × 1012, 1.45 × 108, 9.58 × 106 L mol−1 s−1, activation energies E1–3 = 89.4, 57.82, 86.01 kJ mol−1) and possible synergistic catalysis mechanism of Co/Mo/W active species were first explored.

Efficient calcium sulfite oxidation treatment by a highly active iron-manganese bimetallic metal-organic frameworks (MOFs)

Calcium sulfite (CaSO3) oxidation is the key step in the resource utilization of flue gas desulfurization (FGD) ash waste. However, under natural conditions the oxidation rate of CaSO3 is very low, limiting its conversion into calcium sulfate, an acceptable product for construction material. This study was devoted to the investigation of the synthesis and performance of a bimetallic MOFs with potential catalytic activity, namely, Fe/Mn(BDC)(DMF,F) catalysts. A combination of techniques including SEM, EDS, XRD, FT-IR, etc. were used to characterize the catalysts. The excellent catalytic performance examined in a gas-liquid-solid three-phase oxidation system are due to the special flexible respiratory architecture and homogeneous distribution of active sites, which allows the reactants to fully contact with the catalyst. Mn incorporated in the backbone of the metal-organic framework significantly enriches the catalytic active species that participate in a radical chain reaction with activated SO32- as ·SO3-, which in turn generates the key radical ·SO5- that reacts with SO32- to form SO42-. In the presence of Fe/Mn(BDC)(DMF, F)-13, the oxidation ratio of CaSO3 could reach 90.71%, which is more than 30-fold compared to non-catalytic oxidation and almost 5 times the effects of the single metal Fe(BDC)(DMF, F) catalyst. In addition, the study of kinetics shows that the oxidation rate of Fe/Mn(BDC)(DMF,F)-13 can reach 0.042 mmol·L-1·s-1 with an apparent activation energy of 10.86 kJ/mol. The oxidation rate is mainly affected by reaction temperature, pH value, catalyst concentration, and air flow rate. This study provides a potentially sustainable way for utilization of CaSO3-containing desulfurization ash.

Glucose sensing performance of bimetallic MOFs CoFe-ZIF/CC for enzyme-free saliva sensor applications

Co-ZIF is widely believed as a promising material which shows potential in MOFs based enzyme-free sensors. However, the research of Co-ZIF in glucose sensor filed has been hampered, due to its poor electronic conductivity and slow ion diffusion caused by closed rhombohedral dodecahedron structure. In this work, the obtained Co0.95Fe0.05-ZIF presents highly opened nanosheet structure on CC, resulting in rich open active sites and ions moving channels. Compared with other reported ZIFs, the Co0.95Fe0.05-ZIF/CC exhibits excellent sensing performance with a high sensitivity of 3232.30 μA mM−1 cm−2 in the range of 0.20–1.00 mM and a low detection limit of less than 5 μM, due to its highly opened nanosheet structure. The Co0.95Fe0.05-ZIF/CC also shows excellent selectivity, repeatability and reproducibility for glucose detection. Furthermore, the variation trend of test results measured by this saliva sensor without any sample pre-treatment, is consistent with that of commercial blood glucose meter, indicating its potential in real applications. This synthesis strategy also provides a new direction of structure construction for high performance MOFs in enzyme-free glucose sensor field.

Portable electrochemical sensor for adrenaline detection using CoNi-MOF-based CS-PAM hydrogel

The development of a portable smartphone-based electrochemical sensor for analyzing adrenaline levels in real samples can make a great contribution to the research community worldwide. In order to achieve this goal, the key challenge is to build sensing interfaces with excellent electrocatalytic properties. In this work, microspherical bimetallic metal–organic frameworks (CoNi-MOF) consisting of nanoclusters were first synthesized using a hydrothermal method. On this basis, the catalytic activity of pure chitosan-polyacrylamide hydrogel (CS-PAM) was modulated by adding different amounts of CoNi-MOF during the in-situ synthesis of CS-PAM. Finally, a portable electrochemical detection system based on CS-PAM was established for the detection of adrenaline. A series of resulting composite hydrogels with a large specific surface area, abundant active sites, and unique network structure facilitate the enrichment and catalysis of adrenaline molecules. Under optimal conditions, the analytical platform constructed by using CoNi-MOF-based CS-PAM has the advantages of a wide detection range (0.5–10 and 10–2500 μM), a low detection limit (0.167 μM), and high sensitivity (0.182 and 0.133 μA·μM·cm−2). In addition, the sensor maintains selective detection of the target in the presence of many different types of interferences, and the current response is not significantly reduced even after 60 cycles of testing. We strongly believe that the designed smart portable sensing can realize the accurate determination of adrenaline in complex systems, and this study can provide new ideas for the research of MOFs-based hydrogels in electrochemical analysis.

Spin Crossover and Exchange Effects on Oxygen Evolution Reaction Catalyzed by Bimetallic Metal Organic Frameworks.

Bimetallic metal-organic frameworks (BMOFs) have shown a superior oxygen evolution reaction (OER) performance, attributed to the synergistic effects of dual metal sites. However, the significant role of these dual-metal synergies in the OER is not yet fully understood. In this study, we employed density functional theory to systematically investigate the OER performance of NiAl- and NiFe-based BMOFs by examining all possible spin states of each intermediate across diverse external potentials and pH environments. We found that the spin state featuring a shallow hole trap state and Ni ions with a higher oxidation state serve as strong oxidizing agents, promoting the OER. An external potential-induced spin crossover was observed in each intermediate, resulting in significant changes in the overall reaction and activation energies due to altered energy levels. Combining the constant potential method and the electrochemical nudged elastic band method, we mapped the minimum free energy barriers of the OER under varied external potential and pH by considering the spin crossover effect for both NiAl and NiFe BMOFs. The results showed that NiFe exhibits better OER thermodynamics and kinetics, which is in good agreement with experimentally measured OER polarization curves and Tafel plots. Moreover, we found that the improved OER kinetics of NiFe not only is attributed to lower barriers but also is a result of improved electrical conductivity arising from the synergistic effects of Ni-Fe dual-metal sites. Specifically, replacing the second metal Al with Fe leads to two significant outcomes: a reduction in both the band gap and the effective hole mass compared to NiAl, and the initiation of super- and double-exchange interactions within the Ni-F-Fe chain, thereby enhancing electron transfer and hopping and leading to the improved OER kinetics.

Zinc–cobalt bimetallic metal-organic framework (Zn/Co-MOF) nanoparticles as potent pH stimuli anti-corrosive agent for development of a self-healable epoxy composite coating

The impressive BET-surface area and the design versatility have made Z67(ZIF-67) MOF a potent nanomaterial for anti-corrosion applications. Despite excellent anti-corrosion features the Z67(ZIF-67) suffers poor stability in water media, making it improper for application in polymeric systems. One strategy to enhance the stability of Z67 is its structure modification via a mixed-metal organic framework approach. This study involved the synthesis of a series of Z67 nanoparticles through the incorporation of zinc cation (Zn) at different percentages. Specifically, three different compositions were synthesized: Zn10-Z67, Zn20-Z67, and Zn30-Z67 denoting the addition of 10 %, 20 %, and 30 % molar percent of Zn, respectively. FTIR, FE-SEM, XRD, TEM, ICP-OES, and XPS, as well as BET analyses, were conducted for the Zinc–Cobalt bimetallic MOF structure. Subsequently, the properties attributed to the particles' active and barrier anti-corrosion feature in solution (NaCl) as well as coating (epoxy) phases were investigated. The EIS test performed in the solution phase, after 72h of metal exposure to Zn30-Z67 containing saline media, revealed a 590 % and 30 % increase in total resistance, respectively, compared to the uninhibited sample. Due to the increased stability of Zn10-Z67 in a saline environment, the active corrosion inhibition of the scratched coating containing these particles was increased by approximately 140 % compared to the Z67-containing composite. The incorporation of zinc cations into the structure of Z67 has enhanced the stability and control release features in aqueous environments, thereby enhancing the barrier properties of the epoxy coating. The reduction rate of log|Z|0.01Hz of the Zn10-Z67/EPC was 9 % which was lower than that of the Neat EPC (epoxy coating) (24 %).