Heterobimetallic Synergism in Triple-Redox 2D Framework for Largely Boosted Water Oxidation and Flanked Carboxylic-Acid-Triggered Unconventional Tandem Catalysis.

A fish-bone-shaped and thermochemically stable 2D metal-organic framework (MOF) with multimodal active center-decked pore-wall is devised. Redox-active [Co2(COO)4] node and thiazolo[5,4-d]thiazole functionalization benefit this mixed-ligand MOF exhibiting electrochemical water oxidation with 375 mV overpotential at 10 mA cm-2 current density and 78 mV per dec Tafel slope in alkaline medium. Pair of oppositely oriented carboxylic acids aids postmetalation with transition metal ions to engineer heterobimetallic materials. Notably, overpotential of Ni2+ grafted triple-redox composite reduces to 270 mV with twofold declined Tafel slope than the parent MOF, ranking among the best-reported values, and outperforming majority of related catalysts. Significantly, turnover frequency and charge transfer resistance display 35.5 and 1.4-fold upsurge, respectively, with much uplifted chronopotentiometric stability and increase active surface area owing to synergistic Co(II)-Ni(II) coupling. The simultaneous presence of ─COOH and nitrogen-rich moieties renders this hydrogen-bonded MOF as acid-base synergistic catalyst for recyclable deacetalization-Knoevenagel reaction with >99% product yield under solvent-free mild condition. Besides control experiments, unique role of ─COOH as hydrogen-bond donor site in substrate activation is validated from comparing the performances of molecular-shearing approach-derived structurally similar unfunctionalized MOF, and the heterobimetallic composite. To the best of tandem Knoevenagel condensation, larger-sized acetal exhibits poor yield of α,ß-unsaturated dicyanides, and demonstrates pore-fitting-mediated size-selectivity.

Synergetic Dual-Ion Centers Boosting Metal Organic Framework Alloy Catalysts toward Efficient Two Electron Oxygen Reduction.

Herein, a strategy of synergetic dual-metal-ion centers to boost transition-metal-based metal organic framework (MOF) alloy nanomaterials as active oxygen reduction reaction (ORR) electrocatalysts for efficient hydrogen peroxide (H2 O2 ) generation is proposed. Through a facile one-pot wet chemical method, a series of MOF alloys with unique Ni-M (M-Co, Cu, Zn) synergetic centers are synthesized, where the strong metallic ions 3d-3d synergy can effectively inhibit O2 cleavage on Ni sites toward a favorable two-electron ORR pathway. Impressively, the well-designed NiZn MOF alloy catalysts show an excellent H2 O2 selectivity up to 90% during ORR, evidently outperforming that of NiCo MOF (45%), and NiCu MOF (55%). Moreover, it sustains efficient activity and robust stability under a continuous longterm ORR operation. The correlative in situ synchrotron radiation X-ray adsorption fine structure and Fourier transform infrared spectroscopy analyses reveal at the atomic level that, the higher Ni oxidation states species, regulated via adjacent Zn2+ ions, are favorable for optimizing the adsorption energetics of key *OOH intermediates toward fast two electron ORR kinetics.

Synergetic Cobalt-Copper-Based Bimetal-Organic Framework Nanoboxes toward Efficient Electrochemical Oxygen Evolution.

The development of efficient oxygen electrocatalysts and understanding their underlying catalytic mechanism are of significant importance for the high-performance energy conversion and storage technologies. Herein, we report novel CoCu-based bimetallic metal-organic framework nanoboxes (CoCu-MOF NBs) as promising catalysts toward efficient electrochemical oxygen evolution reaction (OER), fabricated via a successive cation and ligand exchange strategy. With the highly exposed bimetal centers and the well-designed architecture, the CoCu-MOF NBs show excellent OER activity and stability, with a small overpotential of 271 mV at 10 mA cm-2 and a high turnover frequency value of 0.326 s-1 at an overpotential of 300 mV. In combination of quasi in situ X-ray absorption fine structure spectroscopy and density-functional theory calculations, the post-formed CoCu-based oxyhydroxide analogue during OER is believed to account for the high OER activity of CoCu-MOF NBs, where the electronic synergy between Co and neighbouring Cu atoms promotes the O-O bond coupling toward fast OER kinetics.

Comparing Neutral (Monometallic) and Anionic (Bimetallic) Aluminum Complexes in Hydroboration Catalysis: Influences of Lithium Cooperation and Ligand Set.

Bimetallic lithium aluminates and neutral aluminum counterparts are compared as catalysts in hydroboration reactions with aldehydes, ketones, imines and alkynes. Possessing Li-Al cooperativity, ate catalysts are found to be generally superior. Catalytic activity is also influenced by the ligand set, alkyl and/or amido. Devoid of an Al-H bond, iBu2 Al(TMP) operates as a masked hydride reducing benzophenone through a ß-Η transfer process. This catalyst library therefore provides an entry point into the future design of Al catalysts targeting substrate specific transformations.

A CuCo Bimetal Confined Hollow SiC Hybrid Photothermal Nanoreactor for the Integration of Pollutant Mineralization and Solar-Powered Water Evaporation.

Growing attention has been paid to the rational treatment of antibiotics-bearing medical wastewater. However, the complexity of polluted wastewater makes the later comprehensive treatment difficult only by the Advanced Oxidation Process technique. Therefore, the coupled water treatment techniques including contaminant mineralization and regeneration of cleanwater become very attractive. A bimetallic functional hollow nanoreactor defined as (Co@SiO2/Cu-X) was successfully constructed by coating a Cu-doped silica layer on the metal-organic framework (ZIF-67) followed by programmed calcination in nitrogen. The nanoreactor was endowed with a hollow configuration composed of mesoporous N-doping C-Silica hybrid shell encapsulated ultrafine Cu and Co metallic species. Such a configuration allows for the efficient diffusion and open reaction space of big contaminant molecules. The catalytic synergy of exposed Co-Cu bimetals and the easy accessibility of electron-rich contaminants by polar N doping sites triggered surface affinity make the optimal Co@SiO2/Cu-6 afford an excellent catalytic norfloxacin mineralization activity (7 min, kabs=0.744 min-1) compared to Cu-free Co@SiO2-6 (kabs=0.493 min-1) and Co-6 (kabs=0.378 min-1) Benefiting from the above unique advantages, Co@SiO2/Cu-6 show excellent removal performance in degrading different pollutants (carbamazepine, oxytetracycline, tetracycline, and bisphenol A) and persistent recycled stability in removing NFX. In addition, by virtue of the excellent photothermal properties, interfacial solar water evaporation application by Co@SiO2/Cu-6 was further explored to reach the regeneration of cleanwater (1.595 kg m-2 h-1, 97.51 %). The integration of pollutant mineralization and solar water evaporation by creating the monolith evaporation by anchoring the Co@SiO2/Cu-6 onto the tailored melamine sponge allows the regeneration of cleanwater (1.6 kg⋅m-2⋅h-1) and synchronous pollutant removal (NFX, 95 %, 60 min), which provides potential possibility the treatment of complicated wastewater.

Enhancing CO catalytic oxidation performance over Cu-doping manganese oxide octahedral molecular sieves catalyst.

The CO oxidation catalytic activity of catalysts is strongly influenced by the oxygen vacancy defects (OVDs) concentration and the valence state of active metal. Herein, a defect engineering approach was implemented to enhance the oxygen vacancy defects and to modify the valence of metal ions in manganese oxide octahedral molecular sieves (OMS-2) by the introduction of copper (Cu). The characterization and theoretical calculation results reveal that the incorporation of Cu2+ ion into the OMS-2 structure led to a rise in specific surface area and pore volume, weakening of Mn-O bonds, higher proportion of the low-coordinated oxygen species adsorbed in oxygen vacancies (Oads) and an increase in the average oxidation state of manganese. These structural modifications were discovered to considerably reduce the apparent activation energy (Ea), thus ultimately significantly enhancing the CO oxidation activity (T99 at 148 ℃at GHSV = 13,200 h-1) than the original OMS-2 (T99 = 215 ℃ at GHSV = 13,200 h-1). Furthermore, In-situ diffuse reflectance infrared Fourier transform (DRIFT) and In-situ near-ambient pressure X-ray photoelectron spectroscopy (in situ NAP-XPS) results indicate that the bimetallic synergy enhanced by doping strategy accelerates the conversion of oxygen to chemisorbed oxygen species and the reaction rate of CO oxidation through Mn3++Cu2+↔Mn4++Cu+ redox cycle. The findings of this study offer novel perspectives on the design of catalysts with exceptional performance in CO oxidation.

Construction of micro-nano hierarchical wing-like iron/molybdenum oxide heterojunction with synergistic effect for accelerated overall water splitting.

Designing heterojunction catalysts with high-energy interfacial effects, especially combining the geometrical advantages of hierarchical micro-nano structures with the advantages of bi- or multi-metal syergistically optimised electronic coordination environments, is crucial for achieving efficient and stable water splitting. In this study, a simple one-step hydrothermal method was used to construct a hierarchical wing-like iron/molybdenum oxide heterojunction with a porous structure on nickel foam (FMO/NF). The synergistic effect of Fe, Mo, and the heterostructures can enrich structural defects, overcome the disadvantages of the individual components, and improve material performance by optimising the structural configurations and electronic properties and exploiting the electronic interactions that occur between interfaces composed of different phases. In addition, owing to the high porosity of the hierarchical micro-nano structure and abundant active sites, the wing-like FMO/NF was utilised as an efficient bifunctional catalyst for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), presenting low overpotentials of 278.06 and 263.72 mV, respectively, at a current density of 100 mA·cm-2 in 1 mol/L KOH. Furthermore, assembling FMO/NF as both the anode and cathode (FMO/NF || FMO/NF) required a cell voltage of 1.87 V to drive 100 mA·cm-2 in 1 mol/L KOH, and it proceeded continuously for 110 h with negligible cell voltage decay. This work provides a rational synthetic route for the preparation of innovative double transition metal-based micro-nano hierarchical heterostructured electrocatalysts with a synergistic effect and further advances the development of energy-conversion technology.

Promoted selective oxidation of ethylbenzene in liquid phase achieved by hollow CeVO4 microspheres.

Herein, we developed a series of CeVO4 samples with hierarchical hollow microsphere-like structure obtained at different calcination temperatures for the selective oxidation of ethylbenzene (EB) to acetophenone (AcPO) in the presence of TBHP. The optimized catalyst (CVO-500) exhibits a very high yield value of 95.0% (initial reaction rate of 49.4 mmol gcat-1 h-1) under the optimal reaction conditions. Importantly, the representative CVO-500 catalyst presents high stability, with the reaction performance well maintained after five consecutive uses. It has been indicated that the redox V5+/V3+ sites serve as the main active centers, while the electronic interaction and redox transformation between Ce and V facilitates the hopping of V5+/V3+ and the generation of oxygen vacancies. The bimetallic synergy between V and Ce thus endows the CVO-500 catalyst an excellent performance in the EB oxidation reaction. This work paves the way for the exploit of high-performance and cost-effective catalyst for the EB oxidation and beyond.

Amorphous FeNiNbPC nanoprous structure for efficient and stable electrochemical oxygen evolution.

The oxygen evolution reaction (OER) is a crucial process for water splitting. Reducing overpotential is a great challenge because of four electrons transfer and slow kinetics compared to the hydrogen evolution reaction (HER). Highly efficient and stable OER catalyst with low-cost is important for industrial hydrogen production by water splitting. Here we report a simple approach to synthesize free-standing amorphous FexNi77-xNb3P13C7 with the nanoporous structure through electrochemical dealloying. The np-Fe50Ni27Nb3P13C7 exhibits remarkable OER catalytic activity with a low overpotential of 248 mV to achieve the current density of 10 mA cm-2 in 6 M KOH solution. Also, the np-Fe50Ni27Nb3P13C7 exhibits good long-term stability. The improved OER property is due to bimetallic synergy, decreased resistance of charge transfer, nanoporous structure, amorphous nature, and the generation of NiOOH during the OER process. The free-standing amorphous catalysts with nanoporous structure via electrodealloying method provide a promising approach to boost the performance of non-noble metal OER catalysts for the applications.

Bimetallic Ni-Based Catalysts for CO2 Methanation: A Review.

CO2 methanation has recently emerged as a process that targets the reduction in anthropogenic CO2 emissions, via the conversion of CO2 captured from point and mobile sources, as well as H2 produced from renewables into CH4. Ni, among the early transition metals, as well as Ru and Rh, among the noble metals, have been known to be among the most active methanation catalysts, with Ni being favoured due to its low cost and high natural abundance. However, insufficient low-temperature activity, low dispersion and reducibility, as well as nanoparticle sintering are some of the main drawbacks when using Ni-based catalysts. Such problems can be partly overcome via the introduction of a second transition metal (e.g., Fe, Co) or a noble metal (e.g., Ru, Rh, Pt, Pd and Re) in Ni-based catalysts. Through Ni-M alloy formation, or the intricate synergy between two adjacent metallic phases, new high-performing and low-cost methanation catalysts can be obtained. This review summarizes and critically discusses recent progress made in the field of bimetallic Ni-M (M = Fe, Co, Cu, Ru, Rh, Pt, Pd, Re)-based catalyst development for the CO2 methanation reaction.

[Activating Efficiency of Iron-copper Bimetallic Organic Framework MIL-101(Fe,Cu) Toward H2 O2 for Degradation of Dyes].

Practical use of heterogeneous Fenton-like catalysis is inhibited by poor mass transfer and slow conversion of Fe(Ⅲ) to Fe(Ⅱ). In this study, we prepared a novel iron-copper bimetallic organic framework (MIL-101 (Fe,Cu)) using the solvothermal method, and carefully investigated its interfacial characters, catalytic efficacy toward dyes with methylene blue as a model pollutant, and the catalytic activating mechanisms involved in it. The MIL-101(Fe,Cu) exhibited a three-dimensional octahedral shape with a complete crystal structure. The specific BET surface area and average pore size were determined to be as high as 667.2 m2 ·g-1 and 1.9 nm, respectively. These characteristics benefits the exposure of the reactive sites and accelerates mass transfer accordingly. The MIL-101(Fe,Cu)/H2 O2 exhibited promising efficiency toward the degradation of methylene blue in a wide pH range; moreover, at a pH value of 5, the removal efficiency observed was as high as 100% after 20 min of reaction, which was 43.1% and 88.9% higher than that of MIL-101(Fe)/H2 O2 and H2 O2, respectively. Hydroxyl radical ( ·OH) is a dominant active species involved in the degradation of methylene blue using MIL-101(Fe,Cu)/H2 O2 as indicated in radicals quenching experiments. The results of species transformation in Fe and Cu indicated that Cu(Ⅱ) doping provided more active sites, and the Cu(Ⅱ)/Cu(Ⅰ) and Fe(Ⅲ)/Fe(Ⅱ) cycles synergistically facilitated ·OH generation to improve the Fenton-like catalytic efficiency accordingly. The MIL-101(Fe,Cu) as a novel heterogeneous Fenton-like catalyst achieved good performance without any significant pH adjustment and is practically viable for industrial wastewater treatment.