Heterogeneous Transition Metal Catalysts Research Articles

In-situ activation of biomimetic single-site bioorthogonal nanozyme for tumor-specific combination therapy

Copper-catalyzed click chemistry offers creative strategies for activation of therapeutics without disrupting biological processes. Despite tremendous efforts, current copper catalysts face fundamental challenges in achieving high efficiency, atom economy, and tissue-specific selectivity. Herein, we develop a facile “mix-and-match synthetic strategy” to fabricate a biomimetic single-site copper-bipyridine-based cerium metal-organic framework (Cu/Ce-MOF@M) for efficient and tumor cell-specific bioorthogonal catalysis. This elegant methodology achieves isolated single-Cu-site within the MOF architecture, resulting in exceptionally high catalytic performance. Cu/Ce-MOF@M favors a 32.1-fold higher catalytic activity than the widely used MOF-supported copper nanoparticles at single-particle level, as first evidenced by single-molecule fluorescence microscopy. Furthermore, with cancer cell-membrane camouflage, Cu/Ce-MOF@M demonstrates preferential tropism for its parent cells. Simultaneously, the single-site CuII species within Cu/Ce-MOF@M are reduced by upregulated glutathione in cancerous cells to CuI for catalyzing the click reaction, enabling homotypic cancer cell-activated in situ drug synthesis. Additionally, Cu/Ce-MOF@M exhibits oxidase and peroxidase mimicking activities, further enhancing catalytic cancer therapy. This study guides the reasonable design of highly active heterogeneous transition-metal catalysts for targeted bioorthogonal reactions.

Catalytic Applications in the Production of Hydrotreated Vegetable Oil (HVO) as a Renewable Fuel: A Review

The significance and challenges of hydrotreatment processes for vegetable oils have recently become apparent, encompassing various reactions like decarbonylation, decarboxylation, and hydrogenation. Heterogeneous noble or transition metal catalysts play a crucial role in these reactions, offering high selectivity in removing oxygen and yielding desired hydrocarbons. Notably, both sulphided and non-sulphided catalysts exhibit effectiveness, with the latter gaining attention due to health and toxicity concerns associated with sulphiding agents. Nickel-based catalysts, such as NiP and NiC, demonstrate specific properties and tendencies in deoxygenation reactions, while palladium supported on activated carbon catalysts shows superior activity in hydrodeoxygenation. Comparisons between the performances of different catalysts in various hydrotreatment processes underscore the need for tailored approaches. Transition metal phosphides (TMP) emerge as promising catalysts due to their cost-effectiveness and environmental friendliness. Ultimately, there is an ongoing pursuit of efficient catalysts and the importance of further advancements in catalysis for the future of vegetable oil hydrotreatment.

Opinion — On a New Mechamistic Model Toward the Catalytic Reactions: From Hydrogen Combustion to Fischer-Tropsch Reaction

Mechanism research in catalytic chemistry is both fascinating and confusing, particularly when it comes to solid-state catalysts, the nature of catalytic behaviours has been unidentified so far. For a mechanistic model to be acceptable, it should have an ability to explain all unique aspects of a given catalytic reaction and provide an illuminating explanation to a widely range of catalytic reaction. In our recent reports, a new mechanistic model was suggested for catalytic CO<sub>2</sub> reduction reaction on Cu metal and hydrogen evolution reaction on various transition metals, which provides a reasonable interpretation to both catalytic reactions (from the diversity of product distribution and catalytic behaviour of various metals). Here, it is expected to extend this new mechanistic model to a wider range of catalytic reactions over various catalysts. Such as hydrogen combustion with Cu metal adding, oxidation of SO<sub>2</sub> by O<sub>2</sub> to give SO<sub>3</sub> with NO adding, conversion of CO and NO into CO<sub>2</sub> and N<sub>2</sub> with Ru metal adding, and hydrogeneration of propylene with Pt metal adding. Importantly, this model seems also to pertain to the mechanism of the Fischer-Tropsch (T-F) reaction, i.e. the conversion of CO and H<sub>2</sub> to hydrocarbons, principally a mixture of linear alkanes (including methane) and alkenes, by passage over various heterogeneous transition-metal catalysts (Fe, Co, Ni et.al.).

Rational Utilization of Black Phosphorus Nanosheets to Enhance Palladium-Mediated Bioorthogonal Catalytic Activity for Activation of Therapeutics.

Pd-catalyzed chemistry has played a significant role in the growing subfield of bioorthogonal catalysis. However, rationally designing Pd nanocatalysts that show outstanding catalytic activity and good biocompatibility poses a great challenge. Herein, we propose an innovative strategy through exploiting black phosphorous nanosheets (BPNSs) to enhance Pd-mediated bioorthogonal catalytic activity. Firstly, the electron-donor properties of BPNSs enable in situ growth of Pd nanoparticles (PdNPs) on it. Meanwhile, due to the superb capability of reducing PdII , BPNSs can act as hard nucleophiles to accelerate the transmetallation in the decaging reaction process. Secondly, the lone pair electrons of BPNSs can firmly anchor PdNPs on their surface via Pd-P bonds. This design endows Pd/BP with the capability to retard tumor growth by activating prodrugs. This work proposes new insights into the design of heterogeneous transition-metal catalysts (TMCs) for bioorthogonal catalysis.

Evolution of Graphene Supported RuN (N=1–4) Clusters in CO Atmosphere: A First‐Principles Investigation

AbstractWe investigated the evolution of Ru clusters containing 1–4 atoms supported on graphene in CO atmosphere with extensive first principle‐based calculations. Exothermic CO adsorption induces gradual structure reorganization and change of the Ru−Ru, Ru‐graphene, and Ru‐CO interactions within these Ru carbonyls. The upper limits of CO on a surface of Ru cluster are 3, 6, 10 and 12 for Ru1, Ru2, Ru3 and Ru4, respectively. The further CO adsorption enhances steric hindrance at the Ru‐graphene interface that finally leads to release of undercoordinated Ru carbonyls into gas phase. Competing with the CO adsorption and sintering of Ru species for better thermostability, disintegration of multinuclear surface Ru carbonyls to atomically dispersed Ru species on graphene is still feasible. The current findings bring more insights into the evolution and interconversion of Ru carbonyls in a CO atmosphere and may help to understand the superior performance of heterogeneous transition metal catalysts in operation conditions.

Multi-Point Solid-Supported Phosphines for Highly Active Heterogeneous Transition-Metal Catalysts

Multi-Point Solid-Supported Phosphines for Highly Active Heterogeneous Transition-Metal Catalysts

A natural manganese ore as a heterogeneous catalyst to effectively activate peroxymonosulfate to oxidize organic pollutants

Heterogeneous transition metal catalysts are indispensable in improving environmental pollution. However, their fabrication is often costly and cumbersome, and they can easily pollute the environment. This study proposed using a natural Gabonese ore (GBO) containing MnxOy and FexOy as catalysts to degrade orange II (OII) via peroxymonosulfate (PMS) activation. The GBO + PMS system exhibited extraordinarily high stability and catalytic activity towards OII elimination (92.2%, 0.0453 min−1). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging tests and electron spin-resonance (ESR) analysis. Singlet oxygen (1O2) represented the dominant reactive species for OII degradation, while the system presented a lower reaction energy barrier and was effective in a broad pH range (2–10). This work also proposed the activation mechanism for the GBO + PMS system and OII degradation pathways. This study revealed a new approach for exploring inexpensive, eco-friendly, efficient, and stable heterogeneous transition metal catalysts.

Stille, Heck, and Sonogashira coupling and hydrogenation catalyzed by porous-silica-gel-supported palladium in batch and flow

Abstract Owing to their recyclability, heterogeneous transition metal catalysts represent a means of conserving depletable resources for the synthesis of pharmaceutical, agricultural, and functional chemicals. We recently developed a novel heterogeneous palladium catalyst and demonstrated its synthetic availability for Suzuki–Miyaura cross-coupling. Herein, we report the further application of the present catalyst to cross-coupling reactions in batch and flow, as well as a hydrogenative reduction reaction in flow. We demonstrate the flow synthesis for useful material, a liquid crystal, and a 1 h sequential operation of the coupling reaction and hydrogenation reaction.

In situ activation of therapeutics through bioorthogonal catalysis.

Bioorthogonal chemistry refers to any chemical reactions that can occur inside of living systems without interfering with native biochemical processes, which has become a promising strategy for modulating biological processes. The development of synthetic metal-based catalysts to perform bioorthogonal reactions has significantly expanded the toolkit of bioorthogonal chemistry for medicinal chemistry and synthetic biology. A wide range of homogeneous and heterogeneous transition metal catalysts (TMCs) have been reported, mediating different transformations such as cycloaddition reactions, as well as bond forming and cleaving reactions. However, the direct application of 'naked' TMCs in complex biological media poses numerous challenges, including poor water solubility, toxicity and catalyst deactivation. Incorporating TMCs into nanomaterials to create bioorthogonal nanocatalysts can solubilize and stabilize catalyst molecules, with the decoration of the nanocatalysts used to provide spatiotemporal control of catalysis. This review presents an overview of the advances in the creation of bioorthogonal nanocatalysts, highlighting different choice of nano-scaffolds, and the therapeutic and diagnostic applications.

Recent Advances in Catalytic Transfer Hydrogenation with Formic Acid over Heterogeneous Transition Metal Catalysts

Transition-metal-catalyzed transfer hydrogenation with an in situ hydrogen donor has received a great deal of attention from both academia and industry as an alternative to the traditional high-pre...

Adsorption, diffusion and aggregation of Ir atoms on graphdiyne: a first-principles investigation.

Graphdiyne (GDY) is a newly discovered 2D carbon allotrope, widely used as a support for heterogeneous transition metal catalysts. We investigated the binding, electronic structure, diffusion mechanisms and aggregation possibilities of mono-dispersed Ir atoms on GDY by extensive first-principles based calculations. The binding of Ir atoms on GDY can be up to -4.84 eV when the Ir atom is trapped in the C18 ring interacting with 2 adjacent diyne moieties connected to the same benzene ring. The diffusion of Ir atoms along the diyne moiety is quite facile with barriers less than 0.89 eV; the highest barrier for Ir diffusion into the C18 ring is 0.10 eV, whereas inter/intra-C18 ring diffusion is limited by a barrier of 1.64 eV, thereby leading to a dominant population of Ir atoms trapped in the C18 rings. The electronic structure of small Ir clusters was also investigated. Though the formation of Ir-Ir bonds is exothermic and thermodynamically favorable, which may, in some circumstances, even overwhelm the formation of interfacial Ir-C bonds, aggregation of Ir atoms into clusters is limited by the high energy barrier of inter/intra C18 ring diffusion. We propose that aggregation of Ir atoms into clusters may be initiated by shifting the diffusion thermodynamics deliberately and expect the finding may help to understand the stability and evolution of GDY based single atom catalysts.

Recent Achievements in the Hydrogenation of Nitriles Catalyzed by Transitional Metals

Amines are important and valuable intermediates in the pharmaceutical, plastic and agrochemical industry. Hence, there is an increasing interest in developing improved process for the synthesis of amines. The heterogeneous catalytic hydrogenation of nitriles is one of the most frequently applied methods for the synthesis of diverse amines, but the homogeneous catalysis has also received a growing attention from the catalysis community. This mini-review provides an overview of the recent achievements in the selective reduction of nitriles using both homogeneous and heterogeneous transition metal catalysts.

Kinetics and mechanisms of catalytic water oxidation.

The kinetics and mechanisms of thermal and photochemical oxidation of water with homogeneous and heterogeneous catalysts, including conversion from homogeneous to heterogeneous catalysts in the course of water oxidation, are discussed in this review article. Molecular and homogeneous catalysts have the advantage to clarify the catalytic mechanisms by detecting active intermediates in catalytic water oxidation. On the other hand, heterogeneous nanoparticle catalysts have advantages for practical applications due to high catalytic activity, robustness and easier separation of catalysts by filtration as compared with molecular homogeneous precursors. Ligand oxidation of homogeneous catalysts sometimes results in the dissociation of ligands to form nanoparticles, which act as much more efficient catalysts for water oxidation. Since it is quite difficult to identify active intermediates on the heterogeneous catalyst surface, the mechanism of water oxidation has hardly been clarified under heterogeneous catalytic conditions. This review focuses on the kinetics and mechanisms of catalytic water oxidation with homogeneous catalysts, which may be converted to heterogeneous nanoparticle catalysts depending on various reaction conditions.

Selective Heterogeneous Catalytic Hydrogenation of Nitriles to Primary Amines

Primary amines are important intermediates, especially in the area of pharmaceutical, plastic and agrochemical industry. The heterogeneous catalytic hydrogenation of nitriles is one of the most frequently applied process for the synthesis of diverse amines. However, the control of the selectivity is a critical issue in this reaction. Over the past decade, many studies have been reported using heterogeneous transition metal catalysts for the selective reduction of nitriles to the corresponding primary amines. The type of the catalysts, especially, the chemical nature of metals in the catalysts is one of the most important factors to influence the selectivity, the reaction rate, and possibly also the reaction pathway and the deactivation of the catalyst. Thus, this review focuses on the heterogeneous transition metal catalysts and summarizes the recent developments achieved in the selective catalytic hydrogenation of nitriles to primary amines.

Transition Metal Complexes On Insoluble Support And Their Applications In Transformations Of Organic Reactions

In this review we present some important recent work on the catalytic action of some supported transition metal complexes. Different types of synthesized heterogeneous transition metal catalysts including anchoring transition metal complexes on polymer or silica and zeolite encapsulated complexes are discussed, and an overview of their physicochemical characterization techniques are reported. The review is devoted to the catalytic applications of these host-guest materials towards the transformations of some organic reactions e.g. oxidation, epoxidation, hydrolysis, ring-opening…….etc. Key word: Supported transition metal complex catalysts; organic reactions.

Highly Selective Catalytic Reduction of Nitroarenes over Heterogeneous Transition Metal Catalysts: Nano- Catalysts- the New Challenges

A brief review of nano-catalysts application in the reduction of nitro-compounds into corresponding anilines was reported. The influence of the metal nature, catalyst's supports and catalysts particle size in the reaction' selectivity was highlighted. Nano-structure of catalyst advantages was reported evincing future challenges.

N-Alkylation by Hydrogen Autotransfer Reactions [corrected

Owing to the importance of amine/amide derivatives in all fields of chemistry, and also the green and environmentally benign features of using alcohols as alkylating reagents, the relatively high atom economic dehydrative N-alkylation reactions of amines/amides with alcohols through hydrogen autotransfer processes have received much attention and have developed rapidly in recent decades. Various efficient homogeneous and heterogeneous transition metal catalysts, nano materials, electrochemical methods, biomimetic methods, asymmetric N-alkylation reactions, aerobic oxidative methods, and even certain transition metal-free, catalyst-free, or autocatalyzed methods, have also been developed in recent years. With a brief introduction to the background and developments in this area of research, this chapter focuses mainly on recent progress and technical and conceptual advances contributing to the development of this research in the last decade. In addition to mainstream research on homogeneous and heterogeneous transition metal-catalyzed reactions, possible mechanistic routes for hydrogen transfer and alcohol activation, which are key processes in N-alkylation reactions but seldom discussed in the past, the recent reports on computational mechanistic studies of the N-alkylation reactions, and the newly emerged N-alkylation methods based on novel alcohol activation protocols such as air-promoted reactions and transition metal-free methods, are also reviewed in this chapter. Problems and bottlenecks that remained to be solved in the field, and promising new research that deserves greater future attention and effort, are also reviewed and discussed.

Designer Micelles Accelerate Flux Through Engineered Metabolism in E. coli and Support Biocompatible Chemistry.

Synthetic biology has enabled the production of many value-added chemicals via microbial fermentation. However, the problem of low product titers from recombinant pathways has limited the utility of this approach. Methods to increase metabolic flux are therefore critical to the success of metabolic engineering. Here we demonstrate that vitamin E-derived designer micelles, originally developed for use in synthetic chemistry, are biocompatible and accelerate flux through a styrene production pathway in Escherichia coli. We show that these micelles associate non-covalently with the bacterial outer-membrane and that this interaction increases membrane permeability. In addition, these micelles also accommodate both heterogeneous and organic-soluble transition metal catalysts and accelerate biocompatible cyclopropanation in vivo. Overall, this work demonstrates that these surfactants hold great promise for further application in the field of synthetic biotechnology, and for expanding the types of molecules that can be readily accessed from renewable resources via the combination of microbial fermentation and biocompatible chemistry.

ChemInform Abstract: C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation

AbstractReview: 118 refs.

C-Alkylation of Ketones and Related Compounds by Alcohols: Transition-Metal-Catalyzed Dehydrogenation.

Transition-metal-catalyzed C-alkylation of ketones and secondary alcohols, with alcohols, avoids use of organometallic or environmentally unfriendly alkylating agents by means of borrowing hydrogen (BH) or hydrogen autotransfer (HA) activation of the alcohol substrates. Water is formed as the only by-product, thus making the BH process atom-economical and environmentally benign. Diverse homogeneous and heterogeneous transition-metal catalysts, ketones, and alcohols can be used for this transformation, thus rendering the BH process promising for replacing those procedures that use traditional alkylating agents. This Minireview summarizes the advances during the last five years in transition-metal-catalyzed BH α-alkylation of ketones, and β-alkylation of secondary alcohols with alcohols. A discussion on the application of the BH strategy for C-C bond formation is included.