Oxidation of primary alcohols to carboxylic acids is a fundamental reaction in organic chemistry, traditionally dependent on toxic oxidants and often limited by poor selectivity. In this study, we demonstrate the multifunctional capability of some alcohol dehydrogenases (ADHs) to catalyze both alcohol and aldehyde oxidation while regenerating their NAD+ cofactor through concomitant reduction of acetone. Screening of a panel of ADHs revealed that the enzymes from Paracoccus pantotrophus (Pp-ADH) and Aromatoleum aromaticum (Aa-ADH) have strong overoxidation activity to carboxylic acids. The biocatalytic method was assessed for the efficient oxidation of a panel of 27 structurally diverse primary alcohols into carboxylic acids using a single enzyme, with minimal workup and without the need for further purification. The biotransformation was also scaled up using cell-free extracts, while maintaining high yields. In silico studies provided insights into substrate tolerance, highlighting the structural features that govern enzyme activity. This biocatalytic method provides a scalable, selective, and environmentally friendly alternative to conventional oxidation strategies for primary alcohols to carboxylic acids.

The electrochemical reduction of CO2 (CO2RR) offers a promising route for sustainable fuel and chemical production. This study compares the CO2RR performance of hydrothermally synthesized carbon nanosphere-supported nickel hydroxide (Ni-C), copper hydroxide (Cu-C), and bimetallic nickel-copper hydroxide (NiCu-C) catalysts, investigating the influence of metal composition. Significant differences in product selectivity were observed: Cu-C primarily yielded C2 products, whereas Ni-C and NiCu-C generated mixtures of H2, CO, formate, and acetate, with minimal C3 products. Faradaic efficiencies (FEs) for C3 products (including propylene, propane, and n-propanol) were very low for Ni-C and NiCu-C (<0.3% combined). In comparison, Cu-C showed modest FEs (∼3-5%) primarily for n-propanol. X-ray photoelectron spectroscopy revealed partially oxidized nickel species (Ni δ+) in Ni-C and NiCu-C and predominantly Cu(i) species post-reaction, while scanning electron microscopy confirmed a distinct fibrous morphology for the Ni-containing catalysts. Control experiments with CO and acetate, and in situ Raman spectroscopy, suggest reaction pathways that differ from the typical Cu-catalyzed routes, potentially involving hydrogenated intermediates such as *CHO. This work provides a comparative analysis, highlighting how catalyst composition and associated electronic/structural properties influence the overall CO2RR activity and selectivity pathways in Ni, Cu, and NiCu hydroxide systems, rather than achieving significant C3 production.

We present a perspective towards a green synthesis route for synthetic, catechol rich protein analogues (TCC). The method relies on the oxidation of a tyrosine dipeptide in continuous mode by the immobilized tyrosinase SinATyr followed by Michael addition of a dithiol. For the dipeptide substrate a kcat value of 0.16 s−1 and a Km value of 1.6 mM were determined meaning that its conversion is slower and the affinity towards the active center of the enzyme is lower compared to the standard substrate l-tyrosine (kcat = 5.6 s−1; Km = 0.24 mM). For the continuous operation mode SinATyr is immobilized on polyelectrolyte decorated silica microparticles with a k value of 0.11 s−1 (at 1 mM dipeptide substrate) after immobilization and finally experimental proof is given that the converted dipeptide in contact with the dithiol yields the desired TCC structures.

Magnetically induced heating catalysis using encapsulated magnetic nanoparticles as heating agents presents itself as a new efficient method for carrying out high-temperature reactions. In this work, magnetic Fe, Co, and FeCo nanoparticles encapsulated in carbon were synthesized using various methods. Rhenium oxide supported on high-surface-area graphite was used as a catalyst for the gas-phase HDO reaction of anisole, a model molecule for HDO studies of biomass-derived compounds. Characterization confirmed the formation of metallic nanoparticles, the alloying of FeCo and the successful coating with a graphitic-like carbon film around the NPs, resulting in core-shell type materials. According to the catalytic results, the activity and the selectivity were similar when using formic acid (FA) or hydrogen (H2). Furthermore, by comparing the use of conventional and magnetic heating, it was concluded that carbon encapsulation is an effective strategy to generate a bed that heats but does not catalyze. The ReO x catalyst stood out for its capacity to break the OCH3 bond, forming benzene as the major product. Among the different MNPs, FeCo@CHT presented the best properties and performance.

Even though α-arylation of ketones is attractive for direct C–H functionalization of organic substrates, the method largely relies on phosphine-ligated palladium complexes. Only recently, efforts have focused on developing nitrogen-based ligands as a more sustainable alternative to phosphines, with pyridine-functionalized pyridinium amidate (pyr-PYA) N,N′-bidentate ligands displaying good selectivity and activity. Here, we report on a second generation set of catalyst precursors that feature a 5-membered N-heterocycle instead of a pyridine as chelating unit of the PYA ligand to provide less steric congestion for the rate-limiting transmetalation of the enolate. To this end, new heterocycle-functionalized PYA palladium(ii) complexes containing an oxazole (5b), N-phenyl-triazole (5c), N-methyl pyrazole (5d), N-phenyl-pyrazole, (5e), N-xylyl-pyrazole (5f), and N-isopropyl-pyrazole (5g) were synthesized compared to the parent pyr-PYA complex 5a. Less packing of the palladium coordination sphere was evidenced from solid state X-ray diffraction analysis. While the catalytic activity of the oxazole system was lower, all other complexes showed higher activity. In particular, complex 5g comprised of an electron-donating and sterically demanding iPr-pyrazole chelating PYA ligand is remarkably stable towards air and moisture and shows outstanding catalytic activity with complete selectivity (>99% yield) and turnover frequencies up to 1200 h−1, surpassing that of parent 5a by one order of magnitude and rivalling the most active phosphine-based palladium systems. Kinetic studies demonstrate a first order rate-dependence on palladium and the substrate. Some deviation of linearity together with poisoning experiments suggest a mixed homogeneous/heterogeneous pathway, though the reproducible kinetics of in situ catalyst recycling experiments strongly point to a molecularly defined active species, demonstrating the high potential of PYA-based ligands.

Chemical recycling can convert polymers into useful chemicals. Polyolefins can be chemically recycled into their monomers and other hydrocarbons via catalytic pyrolysis or mechano-chemistry. While pyrolysis catalysts are highly active but not selective, mechano-chemistry is more selective but lacks quantitative yields. To address these issues and unlock potential synergies, we herein investigate the effect of zeolite-based pyrolysis catalysts on the conversion of polypropylene during ball milling at room temperature and elevated temperatures, as well as during catalytic kneading. Initially, zeolite catalysts are highly active in the ball mill and their activity is dependent on acid site density. However, they deactivate quickly under the harsh collisions in the ball mill due to the collapse of their crystalline framework. To circumvent deactivation, we used the concept of direct mechano-catalysis and immobilized the zeolite material on surface-roughened grinding spheres. This effectively protects active sites against contact with the container wall or other grinding spheres while allowing contact with polypropylene, leading to sustained catalytic activity and requiring much lower amounts of zeolite. In addition, catalytic kneading of molten polypropylene was investigated as an alternative where energy input is more uniformly distributed in the volume and time compared to highly localized and forceful impacts within the ball mill. Although a synergy of thermo- and mechano-chemical effects was observed initially, the energy intake was limited by a fast decline of melt viscosity due to polymer backbone cleavage. Mechano-chemical conversion and catalytic pyrolysis of polyolefins are two promising platforms for chemical recycling. Our study illustrates the difficulties in combining both and possible pathways to overcome these challenges.

The advancement of electrified chemical processes prompts interest in novel technologies such as plasma-based methane (CH4) conversion into high-demand chemicals. Specifically, nanosecond-pulsed discharges (NPDs) coupled with downstream Pd-based catalysts have demonstrated the best performance in a two-step, integrated process for converting CH4 into ethylene (C2H4). Given the untested composition range involved in this application, the focus of this work is the isolated performance of Pd-based catalysts in typical post-plasma conditions. Extensive campaigns of experiments are run in both traditional and novel stream compositions. The differences with traditional tail-end olefin-rich hydrogenation are highlighted, and a hybrid steady-state kinetic model is proposed, combining the traditional Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach with an improved reversible adsorption methodology. The ability to accurately predict C2H2 hydrogenation kinetics with C2H2-rich and C2H4-poor streams is achieved by the new model, contrary to existing conventional models. Preliminary insights into catalyst optimization for scalable plasma-to-olefin routes are presented.

α-Ketoglutarate-dependent non-haem iron (αKG-NHFe) enzymes play a crucial role in natural product biosynthesis, and in some cases exhibiting multifunctional catalysis capability. This study focuses on αKG-NHFe enzyme FtmOx1, which catalyzes endoperoxidation, dealkylation, and alcohol oxidation reactions in verruculogen biosynthesis. We explore the hypothesis that the conformational dynamics of the active site Y224 confer the multifunctional activities of FtmOx1-catalysis. Utilizing Y224-to-3,5-difluorotyrosine-substituted FtmOx1, produced via the amber codon suppression method, we conducted 19F NMR characterization to investigate FtmOx1's structural flexibility. Subsequent biochemical and X-ray crystallographic analyses provided insights into how specific conformations of FtmOx1-substrate complexes influence their catalytic activities. These findings underscore the utility of 19F NMR as a powerful tool for elucidating the complex mechanisms of multifunctional enzymes, offering potential avenues for developing biocatalytic processes to produce novel therapeutic agents harnessing their unique catalytic properties.

A useful strategy for the co-polymerization of ethylene and functional olefins relies on palladium catalysts, as palladium typically shows in contrast to many other metals a high tolerance to a variety of functional groups. Here we have prepared a set of palladium complexes containing a N,N-bidentate coordinating bis(pyridinium amidate) (bisPYA) ligand. Ligand variation included either para- or an ortho-pyridinium amidate arrangement, with the pyridinium site either sterically flexible or locked through a dimethyl substitution ortho to the amidate. Activation of these complexes with NaBArF in the presence of ethylene indicated that sterically locked ligand structures promoted ethylene conversion and produced polymeric materials. In particular, complex 4d with an ortho-pyridinium amidate bisPYA ligand was active with a production of 10.8 kg polyethylene per mol palladium at room temperature and 1 bar ethylene. Synthesis of the complexes in the presence of K2CO3 or Ag2CO3 afforded adducts in which the K+ or Ag+ ion is bound by the two oxygens of the bisamidate core, thus leading to trimetallic Pd⋯K⋯Pd complexes. Such adduct formation indicates a dual role of NaBArF in halide abstraction and metal sequestration, thus rationalizing the need for 2.5 equivalent of NaBArF per palladium complex for effective polymerization.

In this work, we study the reducibility of a PdO precursor placed by strong electrostatic adsorption on either NiO or SiO2 of NiO/SiO2 obtained by incipient wetness impregnation. The catalysts were characterized by HAADF-STEM, quasi-in situ XPS, CO IR spectroscopy and H2 chemisorption as a function of the reduction temperature and evaluated for their performance in cinnamaldehyde hydrogenation. PdO on SiO2 requires reduction at higher temperatures to achieve appreciable rates of cinnamaldehyde hydrogenation. Pd placed on NiO particles dispersed on the SiO2 support can already be reduced at room temperature and show a higher activity in cinnamaldehyde hydrogenation, which is argued to be due to the higher Pd dispersion obtained at low reduction temperatures.