High Reaction Activity Research Articles

Amine adducts of triallylborane as highly reactive allylborating agents for Cu(I)-catalyzed allylation of chiral sulfinylimines.

The implementation of selective catalytic processes with highly active reagents is an attractive strategy that meets the modern principles of sustainable development of chemistry. In the current study, we for the first time describe the method and general principles of Cu(I)-catalyzed allylation of imines with amine adducts of allylic triorganoboranes. Triallylborane is an extremely reactive compound and cannot be used for the catalytic allylation of imines, whereas its amine adducts are ideal substrates for catalysis. The structure of the amine fragment successfully balances the safety, selectivity and stability of the allylboron reagent, allowing it to demonstrate high activity in catalytic allylation reactions, exceeding many times any known allylboranes. The obtained results are supported by quantitative kinetics data and DFT calculations. The catalytic efficacy of the system was demonstrated on model sulfinylimines (23 examples). High diastereoselectivity up to >99% was achieved, including for the gram-scale synthesis of 2-hydroxyphenyl-derivatives. Taking into account the high reactivity and unsurpassed atom-economy of amine adducts of triallylborane (AAT), they can be considered as prospective allylation reagents with Cu(I) and other appropriate metallocatalysts.

Green reaction engineering towards an iron-based nanostructured hybrid as an electrocatalyst for oxygen evolution reaction

Developing robust electrocatalysts based on nonprecious metals with high activity in the sluggish oxygen-evolution reaction (OER) is crucial for achieving large-scale hydrogen production.

PtCu/Pt core/atomic-layer shell hollow octahedra for oxygen reduction and methanol oxidation electrocatalysis.

Engineering effective bifunctional electrocatalysts that outperform the benchmark Pt/C for direct methanol proton exchange membrane fuel cells is desired and challenging. Here, we designed H-PtCu/PtL OH catalysts with a sub-nanometer Pt(111) shell layer featuring Cu- and Co-vacancies, which exhibited high activity in acidic oxygen reduction and methanol oxidation reactions.

Exploring the impact of abnormal coordination in macrocyclic N-heterocyclic carbene ligands on bio-inspired iron epoxidation catalysis

Macrocyclic and abnormal NHC iron complexes are characterised, showing high catalytic activity in epoxidation reaction and potential for ligand design.

Imine-linked donor–acceptor metal–organic frameworks for an efficient photocatalytic oxidative coupling reaction

We report two imine-linked donor–acceptor (D–A) MOFs with Cu(i) cyclic trinuclear units (CTUs) via Schiff base condensations and their high photocatalytic activity for aerobic oxidation reaction of benzylamines.

Tuning the Ca content of Ni–Ca–Al layered-double hydroxide catalysts for low-temperature CO2 methanation

Ni–Ca–Al LDH-derived catalysts were prepared with different Ca contents for CO2 methanation. The catalysts with up to 6% mol of Ca exhibited a large number of active and basic sites, presenting high activity in low-temperature reactions.

Stable homogeneous silver(I) catalysts for the highly efficient cycloaddition of azides onto terminal alkynes in water.

To develop stable and efficient silver(I) catalysts and evaluate the role of sulfur and phosphorus donor ligands in the catalytic cycloaddition of selected organic azides and alkynes (AAC), a series of mononuclear Ag(I) and heteronuclear Ag(I)-Fe(II) complexes were synthesized. The synthesis utilized phosphine and sulfur donors from the dialkyldithiophosphate and borate families, specifically Na[S2H2B(mt)2]. These complexes are designated as [(dppf)AgSP(S)(OiPr)2] (1), [S2H2B(mt)2Ag(μ-dppf)AgS2H2B(mt)2] (2), [(dppf)Ag(μ-dppf)Ag(dppf)] (3), and [(dppe)AgS2H2B(mt)2] (5). The complexes 1-5 were characterized using a combination of 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, as well as IR spectroscopy techniques. In two instances, single-crystal X-ray diffraction analysis was also employed. Complex 3 exhibited high catalytic activity and regioselectivity in the cycloaddition reaction conducted in water at 40 °C.

Dual Pt atoms stabilized by an optimized coordination environment for propane dehydrogenation

Tailoring atomically dispersed catalysts by various methods has been the subject of intense current research in heterogeneous catalysis. In this work, the structural stability and propane dehydrogenation performance of Pt-TiO2 catalysts with single, dual, and triple Pt atoms doped on the reduced TiO2 surface have been examined. Experimental results indicate the atomically dispersed Pt is thermally very stable and shows exceptionally high activity (TOFpropane = 4.93 s−1) and selectivity (∼98.5 %) for the dehydrogenation reaction. The recently developed machine-learning-based SSW-NN method is then employed to explore the global potential energy surface of the atomically dispersed Pt atom-doped TiO2, which suggests that the single and dual Pt atoms can be tightly held by the vacancies created on the reduced transition-metal oxide, as confirmed by DFT + U calculated energetics. After that, advanced characterization techniques are used in conjunction with microkinetic analysis to establish the quantitative structure–activity relationships. It is found that the dual-Pt-atom structure with two Pt atoms embedded in adjacent Ti and O vacancies is the only active ensemble that dramatically promotes the CH bond activation and hydrogen recombination, as compared to single Pt atoms accommodated by either Ti or O vacancies. These results provide new and direct evidence in support of the idea that specific function can be imparted to specific active sites by tuning their coordination environments, which makes it possible to tailor the catalytic properties of metal oxides to a particular reaction such as propane dehydrogenation.

Regulating Co-O covalency to manipulate mechanistic transformation for enhancing activity/durability in acidic water oxidation.

Developing earth-abundant electrocatalysts with high activity and durability for acidic oxygen evolution reaction is essential for H2 production, yet it remains greatly challenging. Here, guided by theoretical calculations, the challenge of overcoming the balance between catalytic activity and dynamic durability for acidic OER in Co3O4 was effectively addressed via the preferential substitution of Ru for the Co2+ (Td) site of Co3O4. In situ characterization and DFT calculations show that the enhanced Co-O covalency after the introduction of Ru SAs facilitates the generation of OH* species and mitigates the unstable structure transformation via direct O-O coupling. The designed Ru SAs-CoO x catalyst (5.16 wt% Ru) exhibits enhanced OER activity (188 mV overpotential at 10 mA cm-2) and durability, outperforming most reported Co3O4-based and Ru-based electrocatalysts in acidic media.

Installation of superacidic carbon acid moieties into polymer materials via post-polymerization modification.

In the fields of polymer and material chemistries, strong acid units have mainly included sulfonic acids, which has limited the extension of related material chemistries. Here, a unique carbon acid functionality, namely the bis[(trifluoromethyl)sulfonyl]methyl group, was integrated with polymers via a simple postpolymerization modification with the outstandingly electrophilic 1,1-bis[(trifluoromethyl)sulfonyl]ethylene. The proposed synthesis protocol was verified as an efficient process even for solid-state reactions. The synthesis afforded an organic material with a surface decorated with bis[(trifluoromethyl)sulfonyl]methyl units. The fabricated membranes featuring surface bis[(trifluoromethyl)sulfonyl]methyl units functioned as efficient organocatalysts with high catalytic activity for the Mukaiyama aldol reaction. This study provides a simple method for installing superacidic carbon acid moieties onto the surfaces of materials without tedious chemical treatments.

Synthesis and characterization of a green and recyclable arginine-based palladium/CoFe2O4 nanomagnetic catalyst for efficient cyanation of aryl halides.

The utilization of magnetic nanoparticles in the fields of science and technology has gained considerable popularity. Among their various applications, magnetic nanoparticles have been predominantly employed in catalytic processes due to their easy accessibility, recoverability, effective surface properties, thermal stability, and low cost. In this particular study, cyanuric chloride and arginine were utilized to synthesize an arginine-based oligomeric compound (ACT), which was supported on cobalt ferrite, resulting in a green catalyst with high activity and convenient recyclability for the cyanation reaction of aryl halides. The Pd/CoFe2O4@ACT nanomagnetic catalyst demonstrated excellent performance in the cyanation of various aryl iodides and bromides, yielding favorable reaction outcomes at a temperature of 90 °C within a duration of 3 hours. The synthesized nanoparticles were successfully characterized using various techniques, including FTIR, FE-SEM, EDX/MAP, XRD, TEM, TGA, BET, and ICP-OES. Moreover, the Pd/CoFe2O4@ACT catalyst exhibited remarkable catalytic activity, maintaining an 88% performance even after five consecutive runs. Analysis of the reused catalyst through SEM and TEM imaging confirmed that there were no significant changes in the morphology or dispersion of the particles. Ultimately, it was demonstrated that the Pd/CoFe2O4@ACT nanomagnetic catalyst outperformed numerous catalysts previously reported in the literature for the cyanation of aryl halides.

Dy2NiRuO6 perovskite with high activity and durability for the oxygen evolution reaction in acidic electrolyte

This work reports a family of Ru-based perovskites for acid OER. Dy2NiRuO6 displays the highest activity and stability for more than 400 OER cycles. Its high activity is related to short Ru–O bonds and to a surface local ratio of Ni : Ru close to 1 : 1.

Surface activation via selective dealloying of Cu-based metallic glasses for efficient catalytic behavior.

Surface activation is considered to regulate the electronic structures of materials for enhancing catalytic capability. Herein, we report a controllable strategy for constructing three-dimensional micro-nanoporous copper catalysts with high reactivity and activity for the degradation reaction of organic pollutants. Various micro-nanoporous structures and in situ formation processes by chemical selective dealloying of Cu-based metallic glasses are evaluated due to the surface modification. The porous catalysts exhibit superior catalytic performance, attributing to the catalytic mechanisms related to the superior surface activity of nanoscale copper composites and the strong oxidizing capability of activated radicals. These findings will provide a promising synthesis approach for three-dimensional micro-nanoporous catalysts for many chemical reactions.

Efficient solar-driven electrocatalytic nitrate-to-ammonia conversion by 2D ultrathin Fe single-atom catalysts

Ultra-thin 2D Fe-SACs synthesized via a pyrolysis process using a salt template, exhibit high activity for the electrochemical nitrate reduction reaction. Solar cells integrated with 2D Fe-SACs hold great promise for green ammonia production and nitrate removal from water bodies.

Mesoporous hydrogel electrodes with flexible frameworks exhibiting enhanced mass transport for the oxygen evolution reaction.

Mesoporous hydrogel electrodes with unique flexible mesopores surrounded by CoOOH nanosheets were prepared via the electrochemical deposition of hybrid cobalt hydroxide nanosheets, exhibiting high oxygen evolution reaction activity at a high current density owing to the enhanced mass transport of oxygen molecules.

Tuning the performance of Fe-porphyrin aerogel-based PGM-free oxygen reduction reaction catalysts in proton exchange membrane fuel cells.

Fe-N-C catalysts are currently the leading candidates to replace Pt-based catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells. To maximize their activity, it is necessary to optimize their structure to allow high active site density on one hand, and hierarchical porous structure that will allow good mass transport of reactants and products to and from the active sites on the other hand. Hence, the hierarchical structure of the catalyst plays an important role in the balance between the electrochemical active site density and the mass transport resistance. Aerogels were synthesized in this work to study the interplay between these two parameters. Aerogels are covalent organic frameworks with ultra-low density, high porosity, and large surface area. The relative ease of tuning the composition and pore structure of aerogels make them prominent candidates for catalysis. Herein, we report on a tunable Fe-N-C catalyst based on an Fe porphyrin aerogel, which shows high electrocatalytic oxygen reduction reaction activity with tunable hierarchical pore structure and studied the influence of the porous structure on the overall performance in proton exchange membrane fuel cells.

Heterostructured ZnFe2O4@Ni3S2 nanosheet arrays on Ni foam as an efficient oxygen evolution catalyst.

Honeycomb-like ZnFe2O4@Ni3S2 hierarchical nanosheet arrays on Ni foam (NF) were fabricated via a combined hydrothermal and electrodeposition method. The electrode exhibits high oxygen evolution reaction (OER) activity with low overpotentials of 254 mV at 10 mA cm-2 and 290 mV at 50 mA cm-2, a small Tafel slope of 39.29 mV dec-1 and excellent durability in an alkaline electrolyte.

Time-Released Black Phosphorus Hydrogel Accelerates Myocardial Repairing through Antioxidant and Motivates Macrophage Polarization Properties.

The improvement of the myocardial microenvironment largely determines the prognosis of myocardial infarction (MI). After MI, early removal of excessive reactive oxygen species (ROS) in the microenvironment can alleviate oxidative stress injury and promote M2 phenotype polarization of macrophages, which is important for advocating myocardial repair. In this study, we combined traditional natural hydrogel materials chitosan (CS) and gelatin (Gel) to encapsulate polydopamine-modified black phosphorus nanosheets (BP@PDA). We designed an injectable composite gel (CS-Gel-BP@PDA) with a time-released ability to achieve insitu sustained-release BP@PDA in the area of MI. Utilizing the inflammation inhibition ability of CS-Gel itself and the high reactive activity of BP@PDA with ROS, continuous improvement of infarct microenvironment and myocardial repair were achieved. The studies invivo revealed that, compared with the saline group, CS-Gel-BP@PDA group had alleviated myocardial fibrosis and infarct size and importantly improved cardiac function. Immunofluorescence results showed that the ROS level and inflammatory response in the microenvironment of the CS-Gel-BP@PDA group were decreased. In conclusion, our study demonstrated the time-released ability, antioxidative stress activity and macrophage polarization modulation of the novel composite hydrogel CS-Gel-BP@PDA, which provides inspiration for novel therapeutic modalities for MI.

Low-temperature fabrication of potassium single-atom solid base catalysts with high activity in transesterification

Solid base catalysts are appealing to a variety of reactions due to their benefits of easy separation, negligible corrosion, and environmental friendliness. However, their activity is compromised because high temperature is frequently required for the formation of basic sites and aggregation of basic components is easy to occur under those circumstances. Herein, K single-atom solid base catalysts were fabricated by a low temperature, pyrolysis-free, grafting strategy, resulting in the catalysts with highly dispersed basic sites and high activity in transesterification reaction. Potassium tert-butoxide (KTB) functions as the precursor and mesoporous silica SBA-15 is employed as the support, K atoms are successfully grafted onto SBA-15 (denoted as K1/SBA-15) at 30 °C. Various characterizations confirm that highly dispersed K single atoms exist in the form of K-O-Si. The amount of basic sites of K1/SBA-15 measured by titration is 1.62 mmol·g−1, verifying the basicity of the obtained catalyst. K1/SBA-15 shows excellent activity (49.1 % yield) in the transesterification reaction of ethylene carbonate (EC) and methanol to produce dimethyl carbonate (DMC), which is superior to typical alkali metal-related solid superbases. The catalyst was recovered after reaction and the yield of DMC over the recovered catalyst decreases slightly (43.4 %) due to the partial deformation of pores. Moreover, the K1/SBA-15 exhibits a turnover frequency (TOF) value of 82.5 h−1, obviously higher than various reported solid base catalysts (0.95–36.2 h−1) under semblable reaction conditions.

Ethylene Methoxycarbonylation over Heterogeneous Pt1/MoS2 Single-Atom Catalyst: Metal-Support Concerted Catalysis.

Ethylene methoxycarbonylation (EMC) to methyl propanoate (MP) is an industrially important reaction and commercially uses a homogeneous Pd-phosphine organometallic complex as the catalyst and corrosive strong acid as the promoter. In this work, we develop a Pt1/MoS2 heterogeneous single-atom catalyst (SAC) which exhibits high activity, selectivity, and good recyclability for EMC reaction without need of any liquid acid. The production rate of MP achieves 0.35 gMP gcat-1 h-1 with MP selectivity of 91.1% at 1 MPa CO, 1 MPa C2H4, and 160 °C, which can be doubled at 2 MPa CO and corresponds to 320.1 molMP molPt-1 h-1, at least 1 order of magnitude higher than the earlier reported heterogeneous catalyst and even comparable to some of homogeneous catalyst. Advanced characterizations and DFT calculations reveal that all the Pt single atoms are located at the Mo vacancies along the Mo edge of the MoS2 nanosheets, forming pocket-like Mo-S-Pt1-S-Mo ensembles with uniform and well-defined structure. Methanol is first adsorbed and dissociated on Mo sites, and the produced H spillovers to the adjacent Pt site forming Pt-H species which then activate ethylene, forming Pt-ethyl species. Meanwhile, CO adsorbed on the other Mo site reacts with the Pt-ethyl species, yielding propionyl species, and this carbonylation is the rate-determining step. The final methoxylation step proceeds via the nucleophilic attack of propionyl species by -OCH3 affording the final product MP. Such a metal-support concerted catalysis enabled by the Mo-S-Pt1-S-Mo multisite ensemble opens a new avenue for SACs to promote the multimolecular reactions that prevail in homogeneous catalysis.