Monthly Archives: March 2024

Unlocking the Mysteries of Technical Catalyst Deactivation: A View from Space

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Unlocking the Mysteries of Technical Catalyst Deactivation: A View from Space

The paper highlights spatially–resolved characterization techniques for investigating deactivation of technical catalysts. Employing advanced analytical tools, such studies can provide deep insights into the heterogeneous nature of catalyst deactivation. The importance of spatial mapping and scale–bridging analyses is clear to connect observations and understanding of catalyst deactivation from model to technical scale.


Abstract

Modern analytical techniques enable researchers to study heterogeneous catalytic systems at extended length scales and with local probing methods which were previously impractical. Such spatially–resolved analyses are ideal for exploring the complex dynamics governing catalytic activity, and more specifically, deactivation. Here we highlight significant experimental concepts and milestones in the spatially–resolved analysis of technical catalysts, where it is now possible to study catalyst behavior even up to industrially relevant scale. At such extended length scales and in contrast to many model systems, spatial heterogeneities in solid catalyst bodies may play a crucial role in controlling catalytic properties and may be closely linked to catalyst deactivation. Spatially–resolved studies can therefore provide a unique source of information about such local phenomena. Researchers can gain a deeper insight into the operational life of a catalyst by understanding deactivation patterns, which are one of many factors influencing the dynamics of catalytic reactions. In turn, this information promotes the design of more robust and sustainable catalytic systems. We therefore outline the current state of spatially–resolved characterization, together with its role in deconvoluting the complexity of technical catalysts and their deactivation.

Acid‐Free Intermolecular Hydroarylation of Acetylene Catalyzed by Dicationic Palladium(II) and Platinum(II) Ethylene Complexes

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Acid-Free Intermolecular Hydroarylation of Acetylene Catalyzed by Dicationic Palladium(II) and Platinum(II) Ethylene Complexes

The hydroarylation of acetylene is catalyzed by dicationic palladium and platinum pincer complexes [M(PNP)(C2H4)](SbF6)2 (M=Pd and Pt; PNP=2,6-bis(diphenylphosphinomethyl)pyridine). After optimization of reaction conditions, a benchmark of TON 200 is achieved for the catalytic addition of pentamethylbenzene to acetylene with 0.5% [Pd(PNP)(C2H4)](SbF6)2 at room temperature in 24 h under acid-free conditions. Water in small amounts serves as co-catalyst.


Abstract

Four dicationic palladium and platinum ethylene complexes of the type [M(PNP)(C2H4)]X2 (M=Pd, Pt; X=BF4, SbF6, PNP=2,6-bis(diphenylphosphinomethyl)pyridine) were studied as pre-catalysts for the intermolecular hydroarylation of acetylene under acid-free conditions. The palladium complex [Pd(PNP)(C2H4)](SbF6)2 was found to be the most active catalyst for the addition of pentamethylbenzene to acetylene at room temperature. In a 31P NMR spectroscopic study the impact of the counter anion on the rate determining step was demonstrated. Various reaction parameters were screened to optimize the catalytic efficiency. The presence of small amounts of water were beneficial and increased the reaction rate. Water acts as co-catalyst assisting in proton transfer during the catalytic reaction. After optimization of the reaction conditions, a benchmark for the palladium(II) catalyzed hydroarylation of acetylene was achieved with TON 200 at room temperature in 24 h under acid-free conditions. However, this catalytic system has a very limited substrate scope.

Assembly of Titanium‐oxo Clusters from Embonic Acid‐Modified {Ti2} Molecular Building Blocks with Efficient Sulfur‐Catalyzed Oxidation Activities

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Assembly of Titanium-oxo Clusters from Embonic Acid-Modified {Ti2} Molecular Building Blocks with Efficient Sulfur-Catalyzed Oxidation Activities

A family of titanium-oxo clusters were assembled from large-size ligand embonic acid-modified {Ti2} molecular building blocks under solvothermal conditions and Ti20 with a large nuclear number has been used as a stable and heterogeneous catalyst to catalyze sulfur oxidation reactions efficiently.


Abstract

To design and synthesize high-nucleated titanium-oxo clusters rationally based on molecular building blocks with potential coordination ability is still a great challenge. In this work, a family of titanium-oxo clusters, including Ti2 , Ti6 , Ti12 , and Ti20 clusters, have been assembled from large-size ligand embonic acid-modified {Ti2} molecular building blocks under solvothermal conditions. By modulating auxiliary linkers and solvent types, the {Ti2} building blocks exhibit varying degrees of polymerization to form high-nuclear titanium-oxo clusters. Notably, Ti20 with high nucleation, as the decamer containing {Ti2} building blocks, can act as a stable and heterogeneous catalyst to efficiently catalyze the oxidation of sulfides to sulfones and sulfoxides when using H2O2 as the green oxidant. This study provides a new approach for the design and synthesis of highly nucleated and homometallic TOCs based on {Ti2} units.

Securing Reversibility of UVO2+/UVIO22+ Redox Equilibrium in [emim]Tf2N‐Based Liquid Electrolytes towards Uranium Redox‐Flow Battery

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Securing Reversibility of UVO2+/UVIO22+ Redox Equilibrium in [emim]Tf2N-Based Liquid Electrolytes towards Uranium Redox-Flow Battery

Reversibility of a UVO2 +/UVIO2 2+ redox equilibrium in a [emim]Tf2N-based liquid electrolyte was successfully established after addition of DMF and Cl− appropriately. The former was employed to reduce viscosity of the system for improving diffusivity of the U-based electrode active materials, while the latter is also essential to stabilize both UVO2 + and UVIO2 2+ as tetrachloro complexes.


Abstract

We studied electrochemical behavior of UVO2 +/UVIO2 2+ in non-aqueous liquid electrolytes to clarify what is required to attain its reversibility for utilizing depleted U in a redox-flow battery. To transfer knowledge from former pyrochemical systems in high temperature molten salts, 1-ethyl-3-methylimidazolium bis(trifluoromethyl)sulfonylamide ([emim]Tf2N) ionic liquid was employed here. As a result, a reversible redox reaction of the UVO2 +/UVIO2 2+ was successfully observed on a glassy carbon working electrode under presence of Cl− in [emim]Tf2N, where [UVIO2Cl4]2−+e−=[UVO2Cl4]3− occurs after stabilization of both U oxidation states by the Cl− coordination. The observed electrochemical responses are rather sensitive to an electrode material, so that cyclic voltammograms on a Pt working electrode were actually irreversible. To improve diffusivity of solutes, viscosity (η) of [emim]Tf2N diluted with an auxiliary molecular solvent, N,N-dimethylformamide (DMF), was examined under absence and presence of Cl−. When the mole fraction of DMF (x DMF) is 0.769, η of the mixture becomes sufficiently low to be utilized as a liquid electrolyte. Finally, we have succeeded in demonstrating a reversible redox reaction of [UVIO2Cl4]2−+e−=[UVO2Cl4]3− in the [emim]Tf2N-DMF (50 : 50 v/v, x DMF=0.769) liquid electrolyte containing [Cl−]=0.519 M, where η=6.2 mPa ⋅ s.

Chair vs. Boat: Conformational Impacts on DNA Binding Capacity in Cu(II) Complexes Featuring cis‐1,4‐Cyclohexanedicarboxylate

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Chair vs. Boat: Conformational Impacts on DNA Binding Capacity in Cu(II) Complexes Featuring cis-1,4-Cyclohexanedicarboxylate

This work reports the syntheses of two new Cu(II) coordination complexes using cis-1,4 cyclohexanedicarboxylic acid (cis-1,4-H2chdc) linker; and 4,4′-dimethyl-2,2′-bipyridine (1)/5,5′-dimethyl-2,2′-bipyridine (2) auxiliary ligands, wherein, cis-1,4-chdc adopts chair form in 1 and boat conformation in 2. Intriguingly, this conformational change impacts the DNA binding capacities of the complexes as revealed by spectrophotometry, circular dichroism spectroscopy and docking studies.


Abstract

Two new coordination complexes were synthesized, which are formulated as [Cu2(cis-1,4-chdc)(4,4′-Me2bpy)4] ⋅ 2(ClO4 −) ⋅ H2O (1) and [Cu2(cis-1,4-chdc)(5,5′-Me2bpy)4] ⋅ 2(ClO4 −) ⋅ H2O (2), using cis-1,4-cyclohexanedicarboxylic acid (cis-1,4-H2chdc), 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me2bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy). Interestingly, cis-1,4-chdc adopts chair form in 1 and boat conformation in 2. This conformational change impacts the DNA binding capacities of the complexes as revealed by spectrophotometry, circular dichroism (CD) spectroscopy and docking studies. The complex 1 having the chair conformation shows higher affinity towards the DNA base pairs due to anti-alignment of the planar aromatic pyridyl rings of 4,4′-Me2bpy, which strongly intercalates with the adenosine base pairs of DNA by formation of three π–π stacking and two extra π-positive stacking interactions between adenosine bases and positively charged nitrogen. Conversely, 5,5′-Me2bpy with planar aromatic pyridyl rings of complex 2 shows bis-intercalation with weak affinities toward base pairs by formation of two π–π stacking and one π-positive stacking interactions.

Efficient CO2 Electroreduction to CO Facilitated by Porous Ag(111)‐dominant Ag Nanofoams and Cooperative Ionic Liquid Electrolytes

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The application of electrochemical CO2 reduction reaction (CO2RR) to generate value-added products, including carbon monoxide (CO), represents a sustainable strategy for addressing the global carbon balance. Silver (Ag) has gained significant attention as an attractive and cost-effective electrocatalyst for CO2RR-to-CO due to high activity.  Here, the porous Ag nanofoam catalysts with Ag(111)-dominant were prepared by in-situ electrolysis-deposition method in the ionic liquid (IL) electrolyte. The Ag nanofoam catalysts exhibited exceptional activity in converting CO2 to CO, with a high Faradaic efficiency (> 95%) in a wide range of -1.9 ~ -2.4 V vs. Ag/Ag+ in the 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) electrolyte. The maximum CO partial current density of -125.40 mA cm-2 was obtained on this Ag nanofoam catalyst, representing 62% improvement over Ag(110)-dominant Ag electrode (-77.35 mA cm-2) at -2.4 V vs Ag/Ag+ in the [Bmim][BF4] electrolyte. Density functional theory calculations demonstrate that the Ag(111) crystal facet formed by in-situ electrolysis-deposition method prefers to adsorb [Bmim][BF4] which can stabilize the reaction intermediate, thereby weakening the reaction free energy and promoting CO2 electroreduction.

DNA Logic Gates Integrated on DNA Substrates in Molecular Computing

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DNA Logic Gates Integrated on DNA Substrates in Molecular Computing

A new generation of DNA computers is evolving to solve biological and medical problems. DNA logic gates are used to create integrated circuits with biocompatibility and programmability. This minireview highlights the efforts in the development of DNA circuits by integration of DNA logic gates into long chains localized on DNA substrates. This approach of all-DNA integrated circuits (DNA ICs) has the advantage of biocompatibility, increased circuit response due to precise gate localization, increased circuit density, reduced unit concentration, and facilitated cell uptake.


Abstract

Due to nucleic acid's programmability, it is possible to realize DNA structures with computing functions, and thus a new generation of molecular computers is evolving to solve biological and medical problems. Pioneered by Milan Stojanovic, Boolean DNA logic gates created the foundation for the development of DNA computers. Similar to electronic computers, the field is evolving towards integrating DNA logic gates and circuits by positioning them on substrates to increase circuit density and minimize gate distance and undesired crosstalk. In this minireview, we summarize recent developments in the integration of DNA logic gates into circuits localized on DNA substrates. This approach of all-DNA integrated circuits (DNA ICs) offers the advantages of biocompatibility, increased circuit response, increased circuit density, reduced unit concentration, facilitated circuit isolation, and facilitated cell uptake. DNA ICs can face similar challenges as their equivalent circuits operating in bulk solution (bulk circuits), and new physical challenges inherent in spatial localization. We discuss possible avenues to overcome these obstacles.

Aldehyde Reductase Activity of Carboxylic Acid Reductases

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Aldehyde Reductase Activity of Carboxylic Acid Reductases

The synthesis of aldehydes from carboxylic acids is a challenge that the enzyme carboxylic acid reductase (CAR) is mastering. The R-domains of CARs, however, can additionally catalyze carbonyl reduction. This activity is a minor side reaction for many substrate/enzyme pairs but may be significant for others.


Abstract

Carboxylic acid reductase enzymes (CARs) are well known for the reduction of a wide range of carboxylic acids to the respective aldehydes. One of the essential CAR domains - the reductase domain (R-domain) - was recently shown to catalyze the standalone reduction of carbonyls, including aldehydes, which are typically considered to be the final product of carboxylic acid reduction by CAR. We discovered that the respective full-length CARs were equally able to reduce aldehydes. Herein we aimed to shed light on the impact of this activity on aldehyde production and acid reduction in general. Our data explains previously inexplicable results and a new CAR from Mycolicibacterium wolinskyi is presented.

Zinc oxide‐cadmium(II) sulfide heterostructure as a potential photocatalyst for preparing substituted chromenes and its anti‐liver cancer activity

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Zinc oxide-cadmium(II) sulfide heterostructure as a potential photocatalyst for preparing substituted chromenes and its anti-liver cancer activity

Herein, ZnO–CdS is prepared using a green and ecofriendly procedure. The nanomaterial was characterized by FE-SEM, TEM, EDS, DRS, XRD, and FT-IR. The photocatalytic proficiency of ZnO–CdS was then scrutinized in the fabrication of some 4H-chromenes in a mild condition. The outcomes of this study revealed that the nanophotocatalyst has high photocatalytic reactivity and acceptable reusability in the desired condensation reaction. Furthermore, a preliminary in vitro cellular toxicity assay was performed on ZnO–CdS nanoparticles using HepG2 cancer cell line through MTT assay.


There are ongoing studies on the potential use of chromene derivatives in liver cancer therapy. They have shown promising results in preclinical studies for liver cancer, including inhibiting tumor growth and inducing apoptosis. Herein, the nanosized hybrid material zinc oxide (ZnO)–cadmium sulfide (CdS) is prepared using a green and ecofriendly procedure. The nanomaterial was characterized by FE-SEM, transmission electron microscopy, energy dispersive X-ray, DRS, X-ray diffraction, and Fourier transform infrared spectroscopy. The photocatalytic proficiency of ZnO–CdS was then scrutinized in the fabrication of some 4H-chromenes in a mild condition. The outcomes of this study revealed that the nanophotocatalyst has high photocatalytic reactivity and acceptable reusability in the desired condensation reaction. Furthermore, a preliminary in vitro cellular toxicity assay was performed on ZnO–CdS nanoparticles using HepG2 cancer cell line through MTT assay.