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State of the Art in Molecular Catalysis in Europe
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State of the Art in Molecular Catalysis in Europe

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: closed (10 January 2024) | Viewed by 27222

Special Issue Editor

Prof. Dr. Carl Redshaw

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Guest Editor
Department of Chemistry, University of Hull, Hull, UK
Interests: calixarenes; coordination chemistry’ catalysis; polymers; imaging and anti-cancer agents
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

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

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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

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Published Papers (12 papers)

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Editorial

Jump to: Research, Review

3 pages, 163 KiB  
Editorial
State of the Art in Molecular Catalysis in Europe
by Carl Redshaw
Catalysts 2024, 14(7), 459; https://doi.org/10.3390/catal14070459 - 16 Jul 2024
Viewed by 661
Abstract
In this editorial, I would like to provide an overview of the eleven contributions to the Special Issue entitled “State of the Art in Molecular Catalysis in Europe”, which is part of the Organic and Polymer Chemistry Section of Catalysts [...] Full article
(This article belongs to the Special Issue State of the Art in Molecular Catalysis in Europe)

Research

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17 pages, 5572 KiB  
Article
Palladium Complexes Derived from Waste as Catalysts for C-H Functionalisation and C-N Bond Formation
by Khairil A. Jantan, Gregor Ekart, Sean McCarthy, Andrew J. P. White, D. Christopher Braddock, Angela Serpe and James D. E. T. Wilton-Ely
Catalysts 2024, 14(5), 295; https://doi.org/10.3390/catal14050295 - 29 Apr 2024
Viewed by 1843
Abstract
Three-way catalysts (TWCs) are widely used in vehicles to convert the exhaust emissions from internal combustion engines into less toxic pollutants. After around 8–10 years of use, the declining catalytic activity of TWCs causes them to need replacing, leading to the generation of [...] Read more.
Three-way catalysts (TWCs) are widely used in vehicles to convert the exhaust emissions from internal combustion engines into less toxic pollutants. After around 8–10 years of use, the declining catalytic activity of TWCs causes them to need replacing, leading to the generation of substantial amounts of spent TWC material containing precious metals, including palladium. It has previously been reported that [NnBu4]2[Pd2I6] is obtained in high yield and purity from model TWC material using a simple, inexpensive and mild reaction based on tetrabutylammonium iodide in the presence of iodine. In this contribution, it is shown that, through a simple ligand exchange reaction, this dimeric recovery complex can be converted into PdI2(dppf) (dppf = 1,1′-bis(diphenylphosphino)ferrocene), which is a direct analogue of a commonly used catalyst, PdCl2(dppf). [NnBu4]2[Pd2I6] displayed high catalytic activity in the oxidative functionalisation of benzo[h]quinoline to 10-alkoxybenzo[h]quinoline and 8-methylquinoline to 8-(methoxymethyl)quinoline in the presence of an oxidant, PhI(OAc)2. Near-quantitative conversions to the desired product were obtained using a catalyst recovered from waste under milder conditions (50 °C, 1–2 mol% Pd loading) and shorter reaction times (2 h) than those typically used in the literature. The [NnBu4]2[Pd2I6] catalyst could also be recovered and re-used multiple times after the reaction, providing additional sustainability benefits. Both [NnBu4]2[Pd2I6] and PdI2(dppf) were also found to be active in Buchwald–Hartwig amination reactions, and their performance was optimised through a Design of Experiments (DoE) study. The optimised conditions for this waste-derived palladium catalyst (1–2 mol% Pd loading, 3–6 mol% of dppf) in a bioderived solvent, cyclopentyl methyl ether (CPME), offer a more sustainable approach to C-N bond formation than comparable amination protocols. Full article
(This article belongs to the Special Issue State of the Art in Molecular Catalysis in Europe)
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17 pages, 2548 KiB  
Article
Valorization of Chlorella Microalgae Residual Biomass via Catalytic Acid Hydrolysis/Dehydration and Hydrogenolysis/Hydrogenation
by Antigoni G. Margellou, Stylianos A. Torofias, Georgios Iakovou and Konstantinos S. Triantafyllidis
Catalysts 2024, 14(5), 286; https://doi.org/10.3390/catal14050286 - 23 Apr 2024
Cited by 1 | Viewed by 1599
Abstract
Microalgal biomass can be utilized for the production of value-added chemicals and fuels. Within this research, Chlorella vulgaris biomass left behind after the extraction of lipids and proteins was converted to valuable sugars, organic acids and furanic compounds via hydrolysis/dehydration using dilute aqueous [...] Read more.
Microalgal biomass can be utilized for the production of value-added chemicals and fuels. Within this research, Chlorella vulgaris biomass left behind after the extraction of lipids and proteins was converted to valuable sugars, organic acids and furanic compounds via hydrolysis/dehydration using dilute aqueous sulfuric acid as a homogeneous catalyst. Under mild conditions, i.e., low temperature and low sulfuric acid concentration, the main products of hydrolysis/dehydration were monomeric sugars (glucose and xylose) and furanic compounds (HMF, furfural) while under more intense conditions (i.e., higher temperature and higher acid concentration), organic acids (propionic, formic, acetic, succinic, lactic, levulinic) were also produced either directly from sugar conversion or via intermediate furans. As a second valorization approach, the residual microalgal biomass was converted to value-added sugar alcohols (sorbitol, glycerol) via hydrogenation/hydrogenolysis reactions over metallic ruthenium catalysts supported on activated carbons (5%Ru/C). It was also shown that a low concentration of sulfuric acid facilitated the conversion of biomass to sugar alcohols by initiating the hydrolysis of carbohydrates to monomeric sugars. Overall, this work aims to propose valorization pathways for a rarely utilized residual biomass towards useful compounds utilized as platform chemicals and precursors for the production of a wide variety of solvents, polymers, fuels, food ingredients, pharmaceuticals and others. Full article
(This article belongs to the Special Issue State of the Art in Molecular Catalysis in Europe)
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18 pages, 5077 KiB  
Article
Extended Hydrogen-Bonded Molybdenum Arrays Derived from Carboxylic Acids and Dianilines: ROP Capability of the Complexes and Parent Acids and Dianilines
by William Clegg, Mark R. J. Elsegood and Carl Redshaw
Catalysts 2024, 14(3), 214; https://doi.org/10.3390/catal14030214 - 21 Mar 2024
Cited by 1 | Viewed by 1343
Abstract
From reactions involving sodium molybdate and dianilines [2,2′-(NH2)C6H4]2(CH2)n (n = 0, 1, 2) and amino-functionalized carboxylic acids 1,2-(NH2)(CO2H)C6H4 or 2-H2NC6H3 [...] Read more.
From reactions involving sodium molybdate and dianilines [2,2′-(NH2)C6H4]2(CH2)n (n = 0, 1, 2) and amino-functionalized carboxylic acids 1,2-(NH2)(CO2H)C6H4 or 2-H2NC6H3-1,4-(CO2H)2, in the presence of Et3N and Me3SiCl, products adopting H-bonded networks have been characterized. In particular, the reaction of 2,2′-diaminobiphenyl, [2,2′-NH2(C6H4)]2, and 2-aminoterephthalic acid, H2NC6H3-1,4-(CO2H)2, led to the isolation of [(MoCl3[2,2′-N(C6H4)]2}{HNC6H3-1-(CO2),4-(CO2H)]·2[2,2′-NH2(C6H4)]2·3.5MeCN (1·3.5MeCN), which contains intra-molecular N–H∙∙∙Cl H-bonds and slipped π∙∙∙π interactions. Similar use of 2,2′-methylenedianiline, [2,2′-(NH2)C6H4]2CH2, in combination with 2-aminoterephthalic acid led to the isolation of [MoCl2(O2CC6H3NHCO2SiMe3)(NC6H4CH2C6H4NH2)]·3MeCN (2·3MeCN). Complex 2 contains extensive H-bonds between pairs of centrosymmetrically-related molecules. In the case of 2,2′ethylenedianiline, [2,2′-(NH2)C6H4]2CH2CH2, and anthranilic acid, 1,2-(NH2)(CO2H)C6H4, reaction with Na2MoO4 in the presence of Et3N and Me3SiCl in refluxing 1,2-dimethoxyethane afforded the complex [MoCl3{1,2-(NH)(CO2)C6H4}{NC6H4CH2CH2C6H4NH3}]·MeCN (3·MeCN). In 3, there are intra-molecular bifurcated H-bonds between NH3 H atoms and chlorides, whilst pairs of molecules H-bond further via the NH3 groups to the non-coordinated carboxylate oxygen, resulting in H-bonded chains. Complexes 1 to 3 have been screened for the ring opening polymerization (ROP) of both ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) using solvent-free conditions under N2 and air. The products were of moderate to high molecular weight, with wide Ð values, and comprised several types of polymer families, including OH-terminated, OBn-terminated (for PCL only), and cyclic polymers. The results of metal-free ROP using the dianilines [2,2′-(NH2)C6H4]2(CH2)n (n = 0, 1, 2) and the amino-functionalized carboxylic acids 1,2-(NH2)(CO2H)C6H4 or 2-H2NC6H3-1,4-(CO2H)2 under similar conditions (no BnOH) are also reported. The dianilines were found to be capable of the ROP of δ-VL (but not ε-CL), whilst anthranilic acid outperformed 2-aminoterephthalic acid for both ε-Cl and δ-VL. Full article
(This article belongs to the Special Issue State of the Art in Molecular Catalysis in Europe)
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19 pages, 1998 KiB  
Article
Non-Symmetrically Fused Bis(arylimino)pyridines with para-Phenyl Substitution: Exploring Their Use as N′,N,N″-Supports in Iron Ethylene Polymerization Catalysis
by Yizhou Wang, Zheng Wang, Qiuyue Zhang, Yanping Ma, Gregory A. Solan, Yang Sun and Wen-Hua Sun
Catalysts 2024, 14(3), 213; https://doi.org/10.3390/catal14030213 - 21 Mar 2024
Viewed by 1211
Abstract
Through the implementation of a one-pot strategy, five examples of non-symmetrical [N,N-diaryl-11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-diimine]iron(II) chloride complexes (aryl = 2,6-Me2Ph Fe1, 2,6-Et2Ph Fe2, 2,6-i-Pr2Ph Fe3, 2,4,6-Me3Ph Fe4 [...] Read more.
Through the implementation of a one-pot strategy, five examples of non-symmetrical [N,N-diaryl-11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-diimine]iron(II) chloride complexes (aryl = 2,6-Me2Ph Fe1, 2,6-Et2Ph Fe2, 2,6-i-Pr2Ph Fe3, 2,4,6-Me3Ph Fe4, and 2,6-Et2-4-MePh Fe5), incorporating fused six- and seven-membered carbocyclic rings and appended with a remote para-phenyl group, were readily prepared. The molecular structures of Fe2 and Fe3 emphasize the variation in fused ring size and the skewed disposition of the para-phenyl group present in the N′,N,N″-ligand support. Upon activation with MAO or MMAO, Fe1–Fe5 all showed high catalytic activity for ethylene polymerization, with an exceptional level of 35.92 × 106 g (PE) mol−1 (Fe) h−1 seen for mesityl-substituted Fe4/MMAO operating at 60 °C. All catalysts generated highly linear polyethylene with good control of the polymer molecular weight achievable via straightforward manipulation of run temperature. Typically, low molecular weight polymers with narrow dispersity (Mw/Mn = 1.5) were produced at 80 °C (MMAO: 3.7 kg mol−1 and MAO: 4.9 kg mol−1), while at temperatures between 40 °C and 50 °C, moderate molecular weight polymers were obtained (MMAO: 35.6–51.6 kg mol−1 and MAO: 72.4–95.5 kg mol−1). Moreover, analysis of these polyethylenes by 1H and 13C NMR spectroscopy highlighted the role played by both β-H elimination and chain transfer to aluminum during chain termination, with the highest rate of β-H elimination seen at 60 °C for the MMAO-activated system and 70 °C for the MAO system. Full article
(This article belongs to the Special Issue State of the Art in Molecular Catalysis in Europe)
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16 pages, 1874 KiB  
Article
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
by Mark R. J. Elsegood, William Clegg and Carl Redshaw
Catalysts 2023, 13(6), 988; https://doi.org/10.3390/catal13060988 - 9 Jun 2023
Cited by 3 | Viewed by 1659
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 [...] Read more.
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  
Article
Overview of Catalysts with MIRA21 Model in Heterogeneous Catalytic Hydrogenation of 2,4-Dinitrotoluene
by Alexandra Jakab-Nácsa, Viktória Hajdu, László Vanyorek, László Farkas and Béla Viskolcz
Catalysts 2023, 13(2), 387; https://doi.org/10.3390/catal13020387 - 10 Feb 2023
Cited by 3 | Viewed by 2433
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 [...] Read more.
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  
Article
Preformed Pd(II) Catalysts Based on Monoanionic [N,O] Ligands for Suzuki-Miyaura Cross-Coupling at Low Temperature
by Matthew J. Andrews, Sebastian Brunen, Ruaraidh D. McIntosh and Stephen M. Mansell
Catalysts 2023, 13(2), 303; https://doi.org/10.3390/catal13020303 - 29 Jan 2023
Cited by 6 | Viewed by 2178
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 [...] Read more.
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  
Article
Thermally Stable and Highly Efficient N,N,N-Cobalt Olefin Polymerization Catalysts Affixed with N-2,4-Bis(Dibenzosuberyl)-6-Fluorophenyl Groups
by Muhammad Zada, Desalegn Demise Sage, Qiuyue Zhang, Yanping Ma, Gregory A. Solan, Yang Sun and Wen-Hua Sun
Catalysts 2022, 12(12), 1569; https://doi.org/10.3390/catal12121569 - 2 Dec 2022
Viewed by 1836
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 [Mw 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  
Article
Improving Catalytic Activity towards the Direct Synthesis of H2O2 through Cu Incorporation into AuPd Catalysts
by Alexandra Barnes, Richard J. Lewis, David J. Morgan, Thomas E. Davies and Graham J. Hutchings
Catalysts 2022, 12(11), 1396; https://doi.org/10.3390/catal12111396 - 9 Nov 2022
Cited by 7 | Viewed by 3048
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 [...] Read more.
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 molH2O2kgcat−1h−1) approximately 1.7 times that of the bi-metallic analogue (69 molH2O2kgcat−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  
Review
Molecular Catalysts for OER/ORR in Zn–Air Batteries
by Evgeny V. Rebrov and Peng-Zhao Gao
Catalysts 2023, 13(9), 1289; https://doi.org/10.3390/catal13091289 - 10 Sep 2023
Cited by 28 | Viewed by 4135
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 [...] Read more.
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  
Review
Photocatalyzed Oxygenation Reactions with Organic Dyes: State of the Art and Future Perspectives
by Mattia Forchetta, Francesca Valentini, Valeria Conte, Pierluca Galloni and Federica Sabuzi
Catalysts 2023, 13(2), 220; https://doi.org/10.3390/catal13020220 - 18 Jan 2023
Cited by 18 | Viewed by 3871
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. [...] Read more.
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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