Ni-based Metal-organic Framework Research Articles

Metal-organic framework-derived nickel-based catalyst for hydrogen oxidation reaction

Ni-based catalysts with lower activity remain the key to restricting the practical application of anodic hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells. In this work, Ni-based metal-organic frameworks (MOFs) are synthesized and pyrolyzed to prepare high catalytic activity Ni/C HOR catalysts. The carbon substrate generated by the decomposition of the MOFs ligand reduces the Ni2+ into Ni nanoparticles in situ at high temperature, and wraps and confines the Ni nanoparticles. In addition, the graphitized carbon catalyzed by Ni effectively prevents the aggregation of Ni nanoparticles and improves the conduction of electrons. Benefited from the rational design, Ni/C-380 exhibits excellent mass activity (27.1 A g-1 at the overpotential of 50 mV) and exchange current density (1.27 mA cm-2).

Pt Nanoparticles Dispersed on Ni/C Nanoflowers as Stable Electrocatalysts for Methanol Oxidation and Oxygen Reduction

Improving the utilization of Pt by incorporating it in carbon-based materials is a feasible approach to overcome its disadvantages of low abundance and high cost for high-performance electrocatalysis. Herein, we propose a facile strategy to design a highly stable electrocatalyst of Pt–Ni/C by in situ loading Pt nanoparticles with a low ratio of 9.4 wt % onto the Ni/C support. Derived from Ni-based metal–organic frameworks (Ni-MOFs), the three-dimensional porous structure of Ni/C provides a large surface area and uniformly distributed Ni nanoparticles in carbon matrix to facilitate the formation and anchoring of Pt nanoparticles with good adhesion, ultrafine dispersion, and better stability. Benefiting from the good synergistic effect between Pt and Ni/C, this bifunctional Pt–Ni/C electrocatalyst shows outstanding stability toward both oxygen reduction and methanol oxidation reactions during the accelerated durability tests and exhibits improved activity nearly 2 times larger than that of commercial Pt/C. Moreover, the strategy is also employed to prepare different bifunctional electrocatalysts of Pd–Ni/C and Ru–Ni/C with satisfactory results. Therefore, the bifunctional electrocatalysts of M (Pt, Pd, Ru)–Ni/C developed from this in situ loading strategy are expected to be robust electrocatalysts for practical applications in direct methanol fuel cells.

Modulated synthesized Ni-based MOF with improved adsorptive desulfurization activity

Metal-organic frameworks (MOFs) are promising adsorbents for adsorptive desulfurization (ADS) because MOF structure can be tuned to match the application. However, data on the ADS of liquid fuels using Ni-BDC are still scarce. In this study, modulated synthesis was used to prepare a group of Ni-doped MOF absorbents using formic acid as the modulator. The activities of these adsorbents for the ADS of model fuels were investigated, with initial sulfur concentrations of 150, 151, and 153 ppm for thiophene (TH), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6 DMDBT), respectively. Although Ni-doping decreased the crystallinity and crystallite size of the MOFs, the addition of formic acid significantly increased both the crystallite size and crystallinity of all the (xNi/Zn)-BDC materials. In addition, it was observed that modulated synthesis reduced the interpenetration of the MOF-5 crystallites. The adsorption experimental results showed that the modulated synthesis of Ni-BDC using formic acid improved the overall adsorptive activity of Ni-BDC almost twofold. This increase in activity was attributed to increased crystallinity and a higher number of atoms with low coordination for modulated Ni-BDC compared with MOF-5 (100). Formic acid as a modulator was observed to have three effects: i) accelerating MOF synthesis, ii) modulating crystallite size, and iii) controlling crystallinity. The most active adsorbent, Ni-BDC treated with formic acid, was observed to have higher activity toward TH than DBT and 4,6 DMDBT. The overall adsorption capacity and partition coefficient for this adsorbent were 4.14 mg/g and 0.053 mg/g/ppm, respectively.

Efficient microwave absorption of MOFs derived laminated porous Ni@C nanocomposites with waterproof and infrared shielding versatility

Developing high-efficiency electromagnetic wave absorption materials with versatility has been a hotspot and it remains a huge challenge. Here, we reported versatile laminated Ni nanoparticles @ porous carbon (Ni@C) nanocomposites synthesized by a facile carbonization of Ni-based metal-organic frameworks (MOFs) precursor. It was found that the phase components (Ni and C phases) and nano/microstructure (laminated and porous characterizations) were well-modified by controlling the calcination temperature, which led to the variation of the degree of graphitization, magnetic properties, and electromagnetic performances. It showed that the laminated porous Ni@C nanocomposites achieved enhanced microwave absorption performances with a thin thickness of 1.5 mm, a strong reflection loss of −59.8 dB and an effective absorption bandwidth of 4.5 GHz. The underlying microwave absorption mechanism was owing to the improved synergistic effects of polarization relaxation, electron transport, ferromagnetic resonance, as well as multiple reflections and scattering in the laminated porous Ni@C nanocomposites. Furthermore, the multicomponent and laminated porous architecture endowed nanocomposites with favorable waterproof, heat isolation and infrared shielding versatility. Therefore, this work demonstrated a facile approach to develop MOFs-derived versatile laminated porous nanocomposites with efficient microwave absorbing performances.

In Situ Construction of Flexible VNi Redox Centers over Ni-Based MOF Nanosheet Arrays for Electrochemical Water Oxidation.

Atomic-level design and construction of synergistic active centers are central to develop advanced oxygen electrocatalysts toward efficient energy conversion. Herein, an in situ construction strategy to introduce flexible redox sites of VNi centers onto Ni-based metal-organic framework (MOF) nanosheet arrays (NiV-MOF NAs) as a promising oxygen electrocatalyst is developed. The abundant redox VNi centers with flexible metal valence states of V+3/+4/+5 and Ni+3/+2 enable NiV-MOF NAs excellent oxygen evolution reaction (OER) activity and a long-term stability under high current densities, achieving current densities of 10 and 100 mA cm-2 at recorded overpotentials of 189 and 290mV, respectively, and showing ignorable decay of initial activity at 100 mA cm-2 after 100 h OER operation. Operando synchrotron radiation Fourier transform infrared combined with quasi in situ X-ray absorption fine structure spectroscopies reveal at atomic level that the flexible V sites can continuously accept electrons from adjacent active Ni sites to accelerate OER kinetics for NiV-MOF NAs during the reaction process, accompanied by a self-optimized structural distortion of VO6 octahedron for promoting the electrochemical stability.

Self-Nanocavity-Confined Halogen Anions Boosting the High Selectivity of the Two-Electron Oxygen Reduction Pathway over Ni-Based MOFs.

We present a strategy of self-nanocavity confinement for substantially boosting the superior electrochemical hydrogen peroxide (H2O2) selectivity for conductive metal-organic framework (MOF) materials. By using operando synchrotron radiation X-ray adsorption fine structure and Fourier transform infrared spectroscopy analyses, the dissociation of key *OOH intermediates during the oxygen reduction reaction (ORR) is effectively suppressed over the self-nanocavity-confined X-Ni MOF (X = F, Cl, Br, or I) catalysts, contributing to a favorable two-electron ORR pathway for highly efficient H2O2 production. As a result, the as-prepared Br-confined Ni MOF catalyst significantly promotes H2O2 selectivity up to 90% in an alkaline solution, evidently outperforming the pristine Ni MOF catalyst (40%). Moreover, a maximal faradic efficiency of 86% with a high cumulative H2O2 yield rate of 596 mmol gcatalyst-1 h-1 for electrochemical H2O2 generation is achieved by the Br-confined Ni MOF catalyst.

Preparation and Electrochemical Analysis of Ni-Based Metal Organic Frameworks Containing Binary Ligands for Capacitor Electrodes.

As one of the energy storage systems, supercapacitors have quite long charge-discharge cycle life. Among many kinds of electrode materials, metal organic frameworks (MOFs) have unique properties such as high specific surface areas and large pore volume as supercapacitor electrode materials. Nickel-MOFs consist of binary ligand such as 1,3,5-Trimesic acid (H₃BTC) and terephthalic acid (TPA) were used as working electrode materials in three electrode cell for capacitor system. When synthesizing MOFs, it is possible to prepare uniform crystals using hydrothermal synthesis. The morphology of composites was analyzed by field emission scanning electron microscopy (FE-SEM). Electrochemical properties were measured by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) in 6M KOH electrolyte.

Electrocatalytic study of NiO-MOF with activated carbon composites for methanol oxidation reaction

In this work, the methanol oxidation reaction is investigated on Ni based metal organic frameworks (MOF) and its composites with biomass derived activated carbon. NiO-MOF and composites with activated carbon were synthesized using hydrothermal method. SEM, EDX, and XRD, FTIR, TGA techniques were used for characterization of composites. The electrochemical activity of catalysts for oxidation of methanol was tested using cyclic voltammetry (CV) in 1 M KOH and 3 M CH3OH on glassy carbon electrode in three electrode setup. The electrochemical performance shows the effect of activated carbon concentration on methanol oxidation. The electro-oxidation catalyzed by NiO-MOF with activated carbon (40 mg) composite exhibits a peak current density of 182.72 mA/cm2 at 0.89 V potential with a scan rate of 50 mV/s making it a potential catalyst for electrocatalysis of methanol.

Combination of coordinatively unsaturated metal sites and silver nano-particles in a Ni-based metal-organic framework for adsorptive desulfurization

The [email protected] composites were deliberately synthesized with different loading amounts of silver nano-particles in CPO-27-Ni which features unsaturated metal sites and cylindrical one-dimensional channels having a diameter of ca. 11 Å constructed by 2,5-dihydroxybenzene-1,4-dicarboxylate and Ni2+ by a simple one-pot solvothermal method. The well-characterized composites were used as adsorbents to eliminate the aromatic S-compounds of the model oil and fluid catalytic cracking (FCC) oil at room temperature. The experimental results showed that the adsorptive desulfurization followed pseudo-second order reaction kinetics and the adsorptive desulfurization capacity of [email protected] (wherein Ag is 1.23 wt%) was notably enhanced as compared with CPO-27-Ni under the same experimental conditions. Impressively, 35 ppmwS dibenzothiophene (DBT) (or benzothiophene (BT))-containing model oil (20 g) was desulfurized to 2.01 ± 0.27 (or 4.05 ± 0.26) ppmwS by using 0.2 (or 0.5) g of the composite, respectively; the composite showed much higher selectivity factor of adsorbing DBT to naphthalene than CPO-27-Ni. The notable enhancement in adsorptive desulfurization performance is thought to be due to the interactions between Ag particles and sulfur or π-system of thiophene moiety in the S-containing compounds that consequently promote selective attraction between S-containing compounds and the composite. Besides, the composite also showed satisfactory recyclability.

Aspect ratio dependent photocatalytic enhancement of CsPbBr3 in CO2 reduction with two-dimensional metal organic framework as a cocatalyst

All-inorganic CsPbBr3 perovskites have been regarded as promising candidates for photocatalytic CO2 reduction, but the conversion efficiency is limited by serious charge recombination and poor surface reactivity. Herein, a two-dimensional Ni based metal-organic framework (NMF) has been employed as a cocatalyst, which not only acts as an electron extractor in enhancing the electron-hole separation, but also serves as a CO2 capturing agent in facilitating the adsorption and activation of CO2 molecules. As a result, 1.8, 2.5 and 4.1-fold enhancement in CO production has been realized for CsPbBr3 nanocubes, nanorods and nanowires, respectively, which is proved to be positively correlated with the aspect ratio of CsPbBr3. The aspect ratio dependent photocatalytic enhancement is attributed to the increased energy difference at the interface between the conduction band of CsPbBr3 and NMF with the elongation of CsPbBr3, which produces an enlarged driving force for promoted interfacial electron transfer and superior charge separation properties.

Electronic structure modulation with ultrafine Fe3O4 nanoparticles on 2D Ni-based metal-organic framework layers for enhanced oxygen evolution reaction

Two-dimensional (2D) metal organic frameworks (MOFs) are emerging as low-cost oxygen evolution reaction (OER) electrocatalysts, however, suffering aggregation and poor operation stability. Herein, ultrafine Fe3O4 nanoparticles (diameter: 6 ± 2 nm) are homogeneously immobilized on 2D Ni based MOFs (Ni-BDC, thickness: 5 ± 1 nm) to improve the OER stability. Electronic structure modulation for enhanced catalytic activity is studied via adjusting the amount of Fe3O4 nanoparticles on Ni-BDC. The optimal Fe3O4/Ni-BDC achieves the best OER performance with an overpotential of 295 mV at 10 mA cm−2, a Tafel slope of 47.8 mV dec-1 and a considerable catalytic durability of more than 40 h (less than 5 h for Ni-BDC alone). DFT calculations confirm that the active sites for Fe3O4/Ni-BDC are mainly contributed by Fe species with a higher oxidation state, and the potential-determining step (PDS) is the formation of the adsorbed O* species, which are facilitated in the composite.

Common Strategy: Mounting the Rod-like Ni-Based MOF on Hydrangea-Shaped Nickel Hydroxide for Superior Electrocatalytic Methanol Oxidation Reaction.

Developing efficient metal-organic framework (MOF)-based electrocatalysts with improvable activity and persistence toward the methanol oxidation reaction (MOR) is attracting great research attention but still remains an enormous challenge. Herein, a facile strategy, hydrangea-shaped nickel hydroxide template-directed synthesis of the hierarchically structured Ni-MOF on the Ni(OH)2 heterocomposite (denoted as Ni-Ni) for efficient MOR, is developed. The unique hierarchical structure and synergistic effect of the heterocomposite afford more exposed active sites, a facile ion diffusion path, and improved conductivity, favorable for improving MOR catalytic performance. Remarkably, the optimized Ni-Ni-2 material delivers an excellent activity with a high peak current density (24.6 mA cm-2). Furthermore, to prove the universality of this strategy, NixCu1-x(OH)2 isometallic hydroxide was used as the precursor, and a series of MOF-74/CuxNi1-x(OH)2 (denoted as Ni-NiCu) heterogeneous materials have been prepared and could be used as an effective electrocatalyst to catalyze MOR. The results indicate that this strategy can be used in the synthesis of other new composite materials with specific hierarchical structures for a more efficient electrocatalytic system.

Divergent Paths, Same Goal: A Pair-Electrosynthesis Tactic for Cost-Efficient and Exclusive Formate Production by Metal-Organic-Framework-Derived 2D Electrocatalysts.

Electrosynthesis of formic acid/formate is a promising alternative protocol to industrial processes. Herein, a pioneering pair-electrosynthesis tactic is reported for exclusively producing formate via coupling selectively electrocatalytic methanol oxidation reaction (MOR) and CO2 reduction reaction (CO2 RR), in which the electrode derived from Ni-based metal-organic framework (Ni-MOF) nanosheet arrays (Ni-NF-Af), as well as the Bi-MOF-derived ultrathin bismuthenes (Bi-enes), both obtained through an in situ electrochemical conversion process, are used as efficient anodic and cathodic electrocatalysts, respectively, achieving concurrent yielding of the same high-value product at both electrodes with greatly reduced energy input. The as-prepared Ni-NF-Af only needs quite low potentials to reach large current densities (e.g., 100mAcm-2 @1.345V)with ≈100% selectivity for anodic methanol-to-formate conversion. Meanwhile, for CO2 RR in the cathode, the as-prepared Bi-enes can simultaneously exhibit near-unity selectivity, large current densities, and good stability in a wide potential window toward formate production. Consequently, the coupled MOR//CO2 RR system based on the distinctive MOF-derived catalysts displays excellent performance for pair-electrosynthesis of formate, delivering high current densities and nearly 100% selectivity for formate production in both the anode and the cathode. This work provides a novel way to design advanced MOF-derived electrocatalysts and innovative electrolytic systems for electrochemical production of value-added feedstocks.

Enhanced Electrochemical Performance of Bimetallic Doped Ni-Based Metal–Organic Frameworks by Redox Additives in an Alkaline Electrolyte

A Cu2+ and Zn2+ bimetallic doped metal–organic framework Ni2(bdc)2(dabco) (CuZnNi–MOF, where bdc is 1,4-benzenedicarboxylic acid and dabco is 1,4-diazabicyclo[2.2.2]-octane), has been successfully ...

Ni-Based Metal–Organic Framework Nanorods Self-assembled into Hollow Architecture and Decorated with Pt Nanoparticles as Nanocatalysts for CO Oxidation

Herein, we fabricate a new type of Ni-based metal–organic frameworks (Ni-MOFs) with self-assembled nanorods to form hollow architectures, which were then used as excellent supports to load uniform ...

Hollow Ni/C microsphere@graphene foam with dual-spatial and porous structure on the microwave absorbing performance

In this study, a unique dual-spatial three-dimensional (3D) porous structure comprising Ni/C hollow microspheres was prepared from a Ni-based metal organic framework (Ni-MOF) embedded in graphene foam (GF) by the solvothermal method followed by calcination. The graphene foam-based composite, Ni/C@GF (NCGF), exhibited a stable spatial conductive network structure and diverse porous architecture, promoting the microwave absorption (MA) properties of composites. The NCGF with a Ni/C and GF ratio of 1:2.5 displayed a reflection loss (RL) value of ─63 dB with 15 wt% loading, while the thickness is only 1.76 mm. Further, its effective absorption bandwidth (EAB) reached to 5.4 GHz at 2 mm thickness. In addition, when the RL value is less than ─20 dB, the NCGF still manifests a wider bandwidth (2.2 GHz) and a relatively low thickness (1.76 mm). In addition to the extraordinary attenuation ability, the excellent MA performance is mainly ascribed to optimized impedance matching characteristics. Moreover, multiple reflections promoted by the dual-space structure also play a significant role during the microwave absorption process.

Metal organic framework derived hollow NiS@C with S-vacancies to boost high-performance supercapacitors

Transition metal sulfides (TMS) are of great interest as promising battery-type electrode materials, however, the poor conductivity and sluggish reaction kinetics seriously limit their application. Here, we designed a hollow structured precursor of Ni-based metal-organic frameworks (Ni-MOFs) via Ostwald ripening mechanism. Based on this unique precursor, a hollow carbon-coated nickel sulfide nanocrystal (H-NiS1-X/C) with sulfur vacancies was further synthesized through an ion exchange strategy and thermal annealing. By optimizing the content of sulfur source, the sample with appropriate S-vacancies (H-NiS1-X/C-50) was developed. Benefiting from its hollow structure and S-vacancies, this H-NiS1-X/C-50 displayed a high reversible specific capacity (1728 F g−1, 1 A g−1), stable cycling (72% capacity retention over 8000 cycles) and superior rate capability. After assembling the asymmetric supercapacitor, a high energy density of 36.88 Wh kg−1 was achieved. Experimental results and DFT calculations demonstrate that introducing S-vacancies builds an embedded electric field and produces lattice distortions in H-NiS1-X/C, thus enhancing the conductivity of the material. Our strategy also provides a facile way to construct high-performance TMS with unique hollow structure and S-vacancies for developing advanced energy storage devices.

Metal-Organic Framework-Derived Ni-Co@C Catalysts for Urea Oxidation in Urea/H₂O₂ Fuel Cells.

Low-cost Ni-based catalysts have been widely used for urea oxidation in direct urea fuel cells. However, they suffer from issues such as high overpotential, poor stability, and low activity. Herein, we demonstrate the synthesis of a highly porous nanostructured Ni-Co@C catalyst for efficient electrooxidation of urea, via the calcination of Co-doped Ni-based metal-organic framework (Ni/Co-MOF). The porosity of the MOF-derived particles is considerably higher than the Ni/Co-MOF precursor. Furthermore, the Co doping at 30 mol% significantly increases the peak current density and reduces the overpotential of the electro-oxidation of urea. A urea/H₂O₂ fuel cell with Ni0.7Co0.3@C as the anode exhibits maximum power density of 3.4 and 20.0 mW cm-2 with 0.5 M urea in 5 M KOH as anolyte at 25 and 80 °C, respectively. Thus, this work suggests that the highly porous Ni-Co@C catalysts derived from MOF templates can be used for urea oxidation and as efficient anode materials for urea-based fuel cells.

Metal-organic framework precursors derived Ni-doping porous carbon spheres for sensitive electrochemical detection of acetaminophen

The sensitive and selective determination of acetaminophen (AP) in the human body is highly desirable to ensure human health. In this work, nickel-doping nanoporous carbon (Ni/C) was fabricated by directly calcining Ni based metal-organic framework (Ni-MOF). The Ni/C based electrochemical sensor was developed for sensitive and selective determination of AP in human blood serum and urine samples. The prepared Ni/C composite possess plentiful catalytic active sites, ordered mesoporous structure and large specific surface area, which endow the constructed Ni/C sensor with a prominent performance for acetaminophen sensing. Under the optimal conditions, the developed method offered good linearity in the range of 0.20–53.75 μM with a low detection limit (S/N = 3) of 4.04 × 10−2 μM. The electrocatalytic performance of the sensor towards AP was further measured by differential pulse voltammetry and cyclic voltammetry. The results demonstrated that the Ni/C sensor can be feasibly employed for the determination of AP in human blood serum and urine samples with excellent anti-interference stability and good reproducibility. The research reveals a great promising of the Ni/C electrochemical sensor for clinical applications and paves a way for the construction of high-performance electrochemical sensors for AP determination.

Enhanced reduction of aqueous bromate by catalytic hydrogenation using the Ni-based Metal-organic framework Ni(4,4′-bipy)(1,3,5-BTC) with NaBH4

A metal-organic framework catalyst containing immobilized Ni (Ni(4,4′-bipy)(1,3,5-BTC); MOF-Ni) was first synthesized for the enhanced selective reduction of aqueous bromate to environmentally benign bromide, and catalytic reduction was successfully achieved with NaBH4 in a batch reaction system. The reactivity of MOF-Ni for bromate reduction was optimized under different conditions (i.e., catalyst loading, NaBH4 dosage, suspension pH, and coexisting anions). Under the optimized conditions, Ni(4,4′-bipy)(1,3,5-BTC) showed complete bromate removal in 15 min with the fastest bromate reduction kinetics (k = 0.365 min−1) and the highest bromate removal capacity (2.25 mmol·g−1·h−1). The stability and reactivity of Ni(4,4′-bipy)(1,3,5-BTC) for bromate removal were enhanced by decelerating the passivation of MOF-Ni sites with adsorbed active hydrogen species. The material could remove bromate selectively in the presence of coexisting anions with slightly enhanced reactivity. MOF-Ni exhibited 100% removal of bromate throughout 6 continuous cycles of durability testing. Metal leaching from the structure of MOF-Ni was negligible over repeated cycling, and its structure was stable during the continuous reactions, suggesting that durable and stable Ni(4,4′-bipy)(1,3,5-BTC) could be applied to bromate treatment processes in real water and wastewater treatment plants. The experimental results provide a background understanding of the synthesis of a reactive MOF-Ni catalyst for the enhanced reduction of aqueous bromate and the development of novel catalytic water and wastewater treatment processes for the durable and stable selective removal of aqueous bromate.