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Special Issue "State-of-the-Art in Molecular Catalysis in Europe"

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalysis in Organic and Polymer Chemistry".

Deadline for manuscript submissions: 10 January 2024 | Viewed by 10170

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Prof. Dr. Carl Redshaw

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Department of Chemistry, University of Hull, Hull, UK
Interests: calixarenes; coordination chemistry’ catalysis; polymers; imaging and anti-cancer agents
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Dear Colleagues,

Europe remains an important region in the fields of both heterogeneous and homogeneous catalysis, with work including but not limited to catalysts for chemical synthesis, the biorefinery process, environmental solutions, and to possible future sustainable-energy strategies. This Special Issue welcomes both reviews and original research articles on all aspects of heterogeneous and homogeneous catalysis with an emphasis on fundamental and applied research conducted across Europe. Topics include, but are not limited to, the following:

Polyolefin synthesis
Catalysts for biodegradable polymer formation, for example via ring opening polymerization
Catalysts for the conversion of biomass
Catalysts related to the biorefinery process
Homogeneous and heterogeneous catalysis for organic synthesis
Catalysts using CO₂ as a feedstock
Molecular catalysts for electrochemical water splitting
Photocatalytic, photochemical, and photosynthetic systems for H₂ production and CO₂ utilization
Green catalysis, including the use of earth abundant metals
Theoretical studies on any of the above topics

Prof. Dr. Carl Redshaw
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

polyolefin synthesis
catalysts for biodegradable polymer formation, for example via ring opening polymerization
catalysts for the conversion of biomass
catalysts related to the biorefinery process
homogeneous and heterogeneous catalysis for organic synthesis
catalysts using CO₂ as a feedstock
molecular catalysts for electrochemical water splitting
photocatalytic, photochemical, and photosynthetic systems for H₂ production and CO₂ utilization
green catalysis, including the use of earth abundant metals
theoretical studies on any of the above topics

Published Papers (7 papers)

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Research

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16 pages, 1874 KiB

Open AccessArticle

Vanadium Complexes Derived from O,N,O-tridentate 6-bis(o-hydroxyalkyl/aryl)pyridines: Structural Studies and Use in the Ring-Opening Polymerization of ε-Caprolactone and Ethylene Polymerization

Mark R. J. Elsegood

William Clegg

and

Carl Redshaw

Catalysts 2023, 13(6), 988; https://doi.org/10.3390/catal13060988 - 09 Jun 2023

Viewed by 899

Abstract

Interaction of [VO(OiPr)₃] with 6-bis(o-hydroxyaryl)pyridine, 2,6-{HOC(Ph)₂CH₂}₂(NC₅H₃), LH₂, afforded [VO(OiPr)L] (1) in good yield. The reaction of LNa₂, generated in-situ from LH₂ and NaH, with [VCl₃(THF)₃] led to the isolation of [VL₂] (2) in which the pyridyl nitrogen atoms are cis; a regioisomer 3∙2THF, in which the pyridyl nitrogen atoms are trans, was isolated when using [VCl₂(TMEDA)₂]. The reaction of the 2,6-bis(o-hydroxyalkyl)pyridine {HOC(iPr)₂CH₂}₂(NC₅H₃), L¹H₂, with [VO(OR)₃] (R = nPr, iPr) led, following work-up, to [VO(OR)L¹] (R = nPr (4), iPr (5)). Use of the bis(methylpyridine)-substituted alcohol (tBu)C(OH)[CH₂(C₅H₃Me-5)]₂, L²H, with [VO(OR)₃] (R = Et, iPr) led to the isolation of [VO(μ-O)(L²)]₂ (6). Complexes 1 to 6 have been screened for their ability to act as pre-catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL), and rac-lactide (r-LA) and compared against the known catalyst [Ti(OiPr)₂L] (I). Complexes 1, 4–6 were also screened as catalysts for the polymerization of ethylene (in the presence of dimethylaluminium chloride/ethyltrichloroacetate). For the ROP of ε-CL, in toluene solution, conversions were low to moderate, affording low molecular weight products, whilst as melts, the systems were more active and afforded higher molecular weight polymers. For δ-VL, the systems run as melts afforded good conversions, but in the case of r-LA, all systems as melts exhibited low conversions (<10%) except for 6 (<54%) and I (<39%). In the case of ethylene polymerization, the highest activity (8600 Kg·mol·V⁻¹bar⁻¹h⁻¹) was exhibited by 1 in dichloromethane, affording high molecular weight, linear polyethylene at 70 °C. In the case of 4 and 5, which contain the propyl-bearing chelates, the activities were somewhat lower (≤1500 Kg·mol·V⁻¹bar⁻¹h⁻¹), whilst 6 was found to be inactive. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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17 pages, 3470 KiB

Open AccessFeature PaperArticle

Overview of Catalysts with MIRA21 Model in Heterogeneous Catalytic Hydrogenation of 2,4-Dinitrotoluene

Alexandra Jakab-Nácsa

and

Catalysts 2023, 13(2), 387; https://doi.org/10.3390/catal13020387 - 10 Feb 2023

Cited by 1 | Viewed by 1373

Abstract

Although 2,4-dinitrotoluene (DNT) hydrogenation to 2,4-toluenediamine (TDA) has become less significant in basic and applied research, its industrial importance in polyurethane production is indisputable. The aim of this work is to characterize, rank, and compare the catalysts of 2,4-dinitrotoluene catalytic hydrogenation to 2,4-toluenediamine by applying the Miskolc Ranking 21 (MIRA21) model. This ranking model enables the characterization and comparison of catalysts with a mathematical model that is based on 15 essential parameters, such as catalyst performance, reaction conditions, catalyst conditions, and sustainability parameters. This systematic overview provides a comprehensive picture of the reaction, technological process, and the previous and new research results. In total, 58 catalysts from 15 research articles were selected and studied with the MIRA21 model, which covers the entire scope of DNT hydrogenation catalysts. Eight catalysts achieved the highest ranking (D1), whereas the transition metal oxide-supported platinum or palladium catalysts led the MIRA21 catalyst ranking list. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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14 pages, 3941 KiB

Open AccessArticle

Preformed Pd(II) Catalysts Based on Monoanionic [N,O] Ligands for Suzuki-Miyaura Cross-Coupling at Low Temperature

and

Catalysts 2023, 13(2), 303; https://doi.org/10.3390/catal13020303 - 29 Jan 2023

Cited by 1 | Viewed by 1317

Abstract

This paper describes the synthesis and catalytic testing of a palladium complex with a 5-membered chelating [N,O] ligand, derived from the condensation of 2,6-diisopropylphenyl aniline and maple lactone. This catalyst was active towards the Suzuki-Miyaura cross-coupling reaction, and its activity was optimised through the selection of base, solvent, catalytic loading and temperature. The optimised conditions are mild, occurring at room temperature and over a short timescale (1 h) using solvents considered to be ‘green’. A substrate scope was then carried out in which the catalyst showed good activity towards aryl bromides with electron-withdrawing groups. The catalyst was active across a broad scope of electron-donating and high-withdrawing aryl bromides with the highest activity shown for weak electron-withdrawing groups. The catalyst also showed good activity across a range of boronic acids and pinacol esters with even boronic acids featuring strong electron-withdrawing groups showing some activity. The catalyst was also a capable catalyst for the cross-coupling of aryl chlorides and phenylboronic acid. This more challenging reaction requires slightly elevated temperatures over a longer timescale but is still considered mild compared to similar examples in the literature. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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24 pages, 11016 KiB

Open AccessArticle

Thermally Stable and Highly Efficient N,N,N-Cobalt Olefin Polymerization Catalysts Affixed with N-2,4-Bis(Dibenzosuberyl)-6-Fluorophenyl Groups

and

Catalysts 2022, 12(12), 1569; https://doi.org/10.3390/catal12121569 - 02 Dec 2022

Viewed by 1082

Abstract

The cobalt(II) chloride N,N,N-pincer complexes, [2-{(2,4-(C₁₅H₁₃)₂-6-FC₆H₂)N=CMe}-6-(ArN=CMe)C₅H₃N]CoCl₂ (Ar = 2,6-Me₂C₆H₃) (Co1), 2,6-Et₂C₆H₃ (Co2), [...] Read more.

The cobalt(II) chloride N,N,N-pincer complexes, [2-{(2,4-(C₁₅H₁₃)₂-6-FC₆H₂)N=CMe}-6-(ArN=CMe)C₅H₃N]CoCl₂ (Ar = 2,6-Me₂C₆H₃) (Co1), 2,6-Et₂C₆H₃ (Co2), 2,6-i-Pr₂C₆H₃ (Co3), 2,4,6-Me₃C₆H₂ (Co4), 2,6-Et₂-4-MeC₆H₂ (Co5), and [2,6-{(2,4-(C₁₅H₁₃)₂-6-FC₆H₂)N=CMe}₂C₅H₃N]CoCl₂ (Co6), each containing at least one N-2,4-bis(dibenzosuberyl)-6-fluorophenyl group, were synthesized in good yield from their corresponding unsymmetrical (L1–L5) and symmetrical bis(imino)pyridines (L6). The molecular structures of Co1 and Co2 spotlighted their distorted square pyramidal geometries (τ₅ value range: 0.23–0.29) and variations in steric hindrance offered by the dissimilar N-aryl groups. On activation with either MAO or MMAO, Co1–Co6 all displayed high activities for ethylene polymerization, with levels falling in the order: Co1 > Co4 > Co5 > Co2 > Co3 > Co6. Indeed, the least sterically hindered 2,6-dimethyl Co1 in combination with MAO exhibited a very high activity of 1.15 × 10⁷ g PE mol⁻¹ (Co) h⁻¹ at the operating temperature of 70 °C, which dropped by only 15% at 80 °C and 43% at 90 °C. Vinyl-terminated polyethylenes of high linearity and narrow dispersity were generated by all catalysts, with the most sterically hindered, Co3 and Co6, producing the highest molecular weight polymers [M_w range: 30.26–33.90 kg mol⁻¹ (Co3) and 42.90–43.92 kg mol⁻¹ (Co6)]. In comparison with structurally related cobalt catalysts, it was evident that the presence of the N-2,4-bis(dibenzosuberyl)-6-fluorophenyl groups had a limited effect on catalytic activity but a marked effect on thermal stability. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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15 pages, 2144 KiB

Open AccessArticle

Improving Catalytic Activity towards the Direct Synthesis of H₂O₂ through Cu Incorporation into AuPd Catalysts

and

Catalysts 2022, 12(11), 1396; https://doi.org/10.3390/catal12111396 - 09 Nov 2022

Cited by 5 | Viewed by 1922

Abstract

With a focus on catalysts prepared by an excess-chloride wet impregnation procedure and supported on the zeolite ZSM-5(30), the introduction of low concentrations of tertiary base metals, in particular Cu, into supported AuPd nanoparticles can be observed to enhance catalytic activity towards the direct synthesis of H₂O₂. Indeed the optimal catalyst formulation (1%AuPd_(0.975)Cu_(0.025)/ZSM-5) is able to achieve rates of H₂O₂ synthesis (115 mol_H₂O₂kg_cat⁻¹h⁻¹) approximately 1.7 times that of the bi-metallic analogue (69 mol_H₂O₂kg_cat⁻¹h⁻¹) and rival that previously reported over comparable materials which use Pt as a dopant. Notably, the introduction of Cu at higher loadings results in an inhibition of performance. Detailed analysis by CO-DRFITS and XPS reveals that the improved performance observed over the optimal catalyst can be attributed to the electronic modification of the Pd species and the formation of domains of a mixed Pd²⁺/Pd⁰ oxidation state as well as structural changed within the nanoalloy. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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Review

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25 pages, 4827 KiB

Open AccessFeature PaperReview

Molecular Catalysts for OER/ORR in Zn–Air Batteries

Evgeny V. Rebrov

and

Peng-Zhao Gao

Catalysts 2023, 13(9), 1289; https://doi.org/10.3390/catal13091289 - 10 Sep 2023

Viewed by 934

Abstract

Zn–air batteries are becoming the promising power source for small electronic devices and electric vehicles. They provide a relatively high specific energy density at relatively low cost. This review presents exciting advances and challenges related to the development of molecular catalysts for cathode reactions in Zn–air batteries. Bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play the main role in improving performance of reversible fuel cell and metal–air batteries. The catalyst development strategies are reviewed, along with strategies to enhance catalyst performance by application of magnetic field. Proper design of bifunctional molecular ORR/OER catalysts allows the prolongment of the battery reversibility to a few thousand cycles and reach of energy efficiencies of over 70%. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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21 pages, 9725 KiB

Open AccessReview

Photocatalyzed Oxygenation Reactions with Organic Dyes: State of the Art and Future Perspectives

and

Catalysts 2023, 13(2), 220; https://doi.org/10.3390/catal13020220 - 18 Jan 2023

Cited by 7 | Viewed by 1877

Abstract

Oxygen atom incorporation into organic molecules is one of the most powerful strategies to increase their pharmacological activity and to obtain valuable intermediates in organic synthesis. Traditional oxidizing agents perform very well, but their environmental impact and their low selectivity constitute significant limitations. On the contrary, visible-light-promoted oxygenations represent a sustainable method for oxidizing organic compounds, since only molecular oxygen and a photocatalyst are required. Therefore, photocatalytic oxygenation reactions exhibit very high atom-economy and eco-compatibility. This mini-review collects and analyzes the most recent literature on organo-photocatalysis applications to promote the selective oxygenation of organic substrates. In particular, acridinium salts, Eosin Y, Rose Bengal, cyano-arenes, flavinium salts, and quinone-based dyes are widely used as photocatalysts in several organic transformations as the oxygenations of alkanes, alkenes, alkynes, aromatic compounds, amines, phosphines, silanes, and thioethers. In this context, organo-photocatalysts proved to be highly efficient in catalytic terms, showing similar or even superior performances with respect to their metal-based counterparts, while maintaining a low environmental impact. In addition, given the mild reaction conditions, visible-light-promoted photo-oxygenation processes often display remarkable selectivity, which is a striking feature for the late-stage functionalization of complex organic molecules. Full article

(This article belongs to the Special Issue State-of-the-Art in Molecular Catalysis in Europe)

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