Tomas Horsten

After the oxidation of Ni(OH)₂, chloride ions adsorb on the NiOOH surface, leading to OCl⁻ formation through the chlorine oxidation reaction and partial Ni dissolution. In contrast, the presence of a spectator anion layer on NiOOH inhibits chloride adsorption and improves the selectivity of the oxygen evolution reaction.

Water electrolysis is a promising route to green hydrogen production, but its operation in chloride-containing electrolytes (e.g., seawater) is hindered by the competing chlorine evolution reaction (CER) that lowers oxygen evolution reaction (OER) selectivity and accelerates catalyst degradation. Here, we use a combination of electrochemical quartz crystal microbalance (EQCM) and operando Surface-Enhanced Raman spectroscopy (SERS) to directly probe chloride adsorption on Ni-based catalysts. Our study reveals that chloride ions (Cl⁻) adsorb on the Ni surface even at low potentials where Ni(OH)₂ is the predominant phase, and that this adsorption intensifies on high-valent Ni OOH during OER, leading to hypochlorite (OCl⁻) formation significantly reduce OER selectivity and catalyst stability. Importantly, introducing spectator anions such as CO₃ ²⁻, SO₄ ²⁻, or NO₃ ⁻ suppresses Cl⁻ adsorption. Among these, CO₃ ²⁻ binds strongly to Ni sites and inhibits both Cl⁻ and OH⁻ adsorption, whereas SO₄ ²⁻ and NO₃ ⁻, with their weaker binding, preferentially block Cl⁻ while still allowing OH⁻ adsorption. As a result, OCl⁻ generation is dramatically decreased even under locally acidic conditions caused by high OER current densities, thereby enhancing catalyst activity and stability by selectively favoring OER over CER. This study highlights the utility of combined EQCM–SERS analysis to unravel interfacial adsorption processes in complex electrolytes like seawater splitting and provides new insights into leveraging adsorption preferences of spectator anions.

A photocatalytic formal hydrocarbamoylation reaction that employs a cyanate anion as the C1 source and provides N-acyl iminophosphorane products from activated alkenes is described. Mechanistic investigations suggest generation of a phosphoranyl radical by addition of the cyanate anion to a phosphine radical cation, which enables the delivery of the carbamoyl group across alkenes.

Abstract

Catalytic methods that enable functionalization of alkenes with radical intermediates generated from common feedstock chemicals are valuable in synthetic chemistry. In this study, we disclose a photocatalytic formal hydrocarbamoylation strategy for preparation of N-acyl iminophosphorane products from activated alkenes through isocyanate-derived phosphoranyl radicals. Mechanistic investigations suggest generation of the phosphoranyl radical by addition of a cyanate anion to a phosphine radical cation and provide support for its reactivity through the isocyanate moiety. This redox-neutral method enables hydrofunctionalization of diverse alkenylarene and electron-deficient alkene substrates containing sensitive groups such as epoxide, unactivated alkene, amine, or electron-rich and electron-deficient heterocycles. The synthetic versatility of the N-acyl iminophosphorane functionality is demonstrated through one-step conversion to other valuable nitrogen-containing functional groups.

Nature Chemistry, Published online: 21 November 2025; doi:10.1038/s41557-025-01987-6

Catalytic aerobic oxidation under aqueous alkaline conditions promotes C–C cleavage in pine- and poplar-derived lignin oligomers, accessing high yields of aromatic monomers. The monomeric phenols obtained from this process then undergo effective biological conversion into cis,cis-muconic acid and 2-pyrone-4,6-dicarboxylic acid using engineered strains of Pseudomonas putida.

Abstract

Existing methods for lignin deconstruction to aromatic monomers primarily cleave carbon–oxygen bonds within the polymer, resulting in sub-optimal monomer yields and formation of oligomers that retain intact carbon–carbon bonds. Here, we demonstrate that copper-catalyzed aerobic oxidation under aqueous alkaline conditions promotes oxidative cleavage of carbon–carbon bonds in lignin oligomers derived from reductive catalytic fractionation (RCF) of pine and poplar biomass. Fundamental insights are gained from reactions of model compounds that resemble subunits present in RCF oligomers. Optimal results are achieved in a flow reactor that provides precise control over O₂ delivery, temperature, and reaction residence time. The Cu-catalyzed aerobic oxidation conditions access aromatic monomers in 19 and 34 wt% monomer yields, respectively, from pine- and poplar-derived RCF oligomers. Overall, the sequence consisting of biomass RCF into monomers and oligomers followed by oxidative deconstruction of the RCF oligomers generates substantially higher yields of aromatic monomers from lignin. Engineered strains of Pseudomonas putida support biological funneling of the oligomer-derived oxygenated aromatic compounds into cis,cis-muconic acid from pine or 2-pyrone-4,6-dicarboxylic acid from poplar.

Aryl boronic acids are key in building new molecules, but their direct conversion to radicals with electricity has been challenging. This work uses alternating polarity electrolysis and fluoride to form easier-to-oxidize organoboron intermediates, enabling efficient radical generation. For highly electron-deficient substrates, phosphite mediation happens offering a versatile way for electrochemical functionalization of aryl boronic acids.

Aryl organoboron reagents play an important role in modern organic synthesis, and interest in radical-based coupling reactions from these precursors has grown rapidly. However, direct electrochemical generation of aryl radicals from aryl boronic acids, ArB(OH)₂, remains understudied due to their high oxidation potentials (E _ox > 2 V vs. Fc/Fc⁺) and challenges associated with electrochemical processes such as electrode passivation. Aryl potassium trifluoroborate salts (ArBF₃K) can be oxidized efficiently to aryl radicals is previously reported using alternating polarity electrolysis. Building on this, it is combined alternating polarity electrosynthesis with in situ fluoride activation to generate redox-active aryl fluoroborate intermediates, ArBF(OH)₂ and/or ArBF₂(OH), which have significantly lower oxidation potentials than their parent boronic acids or trifluoroborates. Moreover, it is found that for highly electron deficient aryl boronic acids with oxidation potentials higher than 1.7 V versus Fc/Fc⁺, a different mechanism is proposed where aryl boronic acids underwent ipso-substitution with oxidatively generated P(OEt)₃ radical cation. Overall, this dual mechanistic pathway allows an efficient radical-based functionalization of a broad range of aryl boronic acids to form aryl CP bonds.

In this work, we report a novel light-mediated desaturation strategy enabled by electron donor–acceptor complex formation. DFT and mechanistic studies reveal that the reaction proceeds via single-electron transfer, hydrogen atom transfer, and base-mediated deprotonation sequentially with pyridinium salt serving dually as oxidant and base, and hexafluoroisopropanol functioning as solvent and radical mediator. Notably, this strategy demonstrates broad substrate scope, enabling efficient synthesis of quinolinones, coumarins, and flavones, and also facilitates the late-stage functionalization of drug molecules.

Abstract

Recently, electron donor–acceptor (EDA) complex-mediated organic synthetic strategies have emerged as powerful tools for diverse bond-forming transformations; however, their efficiency often diminishes when ionic reactants are involved. This limitation arises from the requirement of polar solvents such as DMSO or DMF to solubilize ionic species for the formation of effective EDA complex. Consequently, these solvents engage in competing EDA complex formation or disrupt ionization equilibria. In parallel, there is a pressing necessity of modern and efficient strategy to achieve dehydrogenation reactions, which are in general limited by the drawbacks of traditional approaches. To address both, herein, we disclose an innovative desaturation strategy based on the formation of an EDA complex between a dihydrogenated organic substrate and an N-methoxy pyridinium salt. In our study, solubility issues, which are associated with the pyridinium salt, are effectively addressed by using hexafluoroisopropanol (HFIP). Beyond enhancing solubility, HFIP also functions as a transient H-shuttle, significantly reducing the activation energy for this transformation. This cooperative interplay between HFIP and the pyridinium salt enables the efficient and selective desaturation of a broad range of heterocyclic carbonyl compounds—including quinolinones, coumarins, and flavones—which are valuable scaffolds in pharmaceutical and agrochemical research. At the end, detailed mechanistic studies with the aid of experiments as well as DFT studies clearly disclose the mechanism as well as the important role of HFIP in this reaction.

Double trouble lignin is first reductively depolymerized with a palladium catalyst to form smaller lignin macromolecules enriched in phenolic hydroxyl groups. Afterward, these macromolecules are exposed to Co(salen)-catalyzed oxidative cleavage, initiated at the phenolic OH sites, to form benzoquinones and benzaldehydes.

This study investigates a tandem Pd-catalyzed reductive depolymerization of lignin and subsequent Co(salen)-catalyzed oxidative cleavage to obtain benzoquinones and benzaldehydes. The reductive depolymerization will result in lignin macromolecules with heavily increased phenolic OH content, which are then selectively cleaved by the Co(salen) catalyst to yield benzoquinones and benzaldehydes. Compared to lignin samples that do not undergo reductive depolymerization first, benzoquinone yields are substantially increased.

The development of a two-stage process for converting CO₂ via CH₄ to C₆H₆ using a Ni/TiO₂ catalyst in stage 1 and a Mo/ZSM-5 catalyst stage 2. Thermodynamic calculations as well as experimentally varying parameters, aided in finding the optimal reaction conditions and reducing the coke deposition in stage 2. Furthermore, operando spectroscopy was employed to understand the increased catalyst stability in stage 2.

Abstract

In the refinery of the future, the input shifts from crude oil to biomass, plastic, and CO₂. Therefore, we need to find alternative routes to produce chemical building blocks, such as aromatics, which are used in products like, for example, fuels. In this study, we investigated a two-stage route to produce benzene from CO₂. In two sequential reactions, CO₂ is first converted into methane over a Ni/TiO₂ catalyst, and methane is further reacted to yield benzene using a Mo/ZSM-5 catalyst via the methane dehydroaromatization (MDA) reaction. Through a combination of thermodynamic calculations and experiments, we found the goldilocks conditions for performing this two-stage process. The unreacted CO₂ and H₂ from the first reaction extended the benzene production in the second reaction. Using a reaction mixture of CO₂, H₂, and CH₄ resulted in benzene production of at least 72 h, by suppressing carbon growth on the catalyst surface. However, the concentration range in which CO₂ and H₂ can be added to the feed without losing benzene production is narrow, as we show with H₂ fluctuation experiments. We demonstrate that the combination of CO₂ methanation and MDA allows us to catalytically convert CO₂ into benzene with an overall yield of 5%.

This review focuses on the frontier field of catalytically transforming lignin and its depolymerization products into high-value natural bioactive compounds. It systematically summarizes recent research advances in the efficient conversion of lignin-derived aromatic monomers into various important natural products.

Lignin, as the most abundant renewable aromatic polymer in nature, holds significant potential for the sustainable synthesis of high-value natural bioactive compounds (NBCs). However, current research exhibits a disjointed approach, in which upstream lignin depolymerization processes remain disconnected from downstream catalytic synthesis of these medicinally and nutritionally valuable chemicals. Consequently, most studies are limited to using lignin model derivatives as substrates. Furthermore, existing literature on synthesizing natural active components from lignin and its derivatives is fragmented and lacks comprehensive reviews. To address this gap, this review first outlines lignin depolymerization methods and their resulting primary aromatic monomers. Subsequently, following the classification framework of NBCs, it systematically evaluates recent advances in synthesizing high-value natural products (e.g., flavonoids, curcumin analogs, and tetrahydroisoquinolines) from lignin and its derived feedstocks using chemo-catalytic, biocatalytic, and chemo-bio cascade strategies. This integrated analysis aim is to bridge upstream depolymerization with downstream conversion processes, providing theoretical guidance and technical references for enhancing lignin valorization and enabling accelerated synthesis of NBCs from lignin.

The Cover Feature shows a chameleon that changes color upon light irradiation similar to the light-responsive liquid crystal film described in the Research Article by H. Q. Trân and B. J. Ravoo (DOI: 10.1002/chem.202501851). With green or orange light, the liquid crystal is nematic and birefringent, displaying bright colors under crossed polarizers; with red or UV light, the liquid crystal turns isotropic and appears black under crossed polarizers.

In this study, the surface orientation of chiral double-L (CDL) DNA origami on mica was controlled by tuning magnesium ion (Mg²⁺) concentration. This simple yet powerful method, exploiting global shape distortions, achieved 100% S orientation enabling precise nanostructure deposition.

Abstract

Controlling the surface orientation of DNA origami nanostructures (DON) is crucial for applications in nanotechnology and materials science. While previous work utilized various DON modifications, simple methods for controlling their landing orientation remain scarce. Here, we demonstrate a straightforward approach to control the adsorption orientation of chiral double-L (CDL) DON on mica by tuning magnesium ion (Mg²⁺) concentration and exploiting global shape distortions. Using atomic force microscopy (AFM), we analyzed the resulting distribution of the mirror-image orientations, referred to as S and Z orientations, at both buffer/mica and air/mica interfaces and identified conditions resulting in homogenous CDL orientation of 100% S. These results demonstrate how DON conformation and ionic environments influence DON orientation, offering insights for precise nanostructure deposition.

A mild, scalable electrocatalytic method for direct lactonization of benzylic alcohols to phthalides using N-hydroxyphthalimide as a redox mediator is reported. This metal-free process proceeds via a phthalimide-N-oxyl-mediated hydrogen atom transfer mechanism, shows broad scope with good to excellent yields, and enables late-stage functionalizations, including syntheses of talopram and a Y5 receptor antagonist intermediate.

A sustainable and efficient electrochemical method for the direct oxidative lactonization of benzylic alcohols, enabling rapid access to isobenzofuran-1(3H)-ones (phthalides) is presented. This electrocatalytic transformation leverages N-hydroxyphthalimide as a redox mediator under mild, metal-free conditions, offering an environmentally friendly alternative to traditional oxidation protocols. The method demonstrates broad substrate scope and delivers phthalide derivatives consistently in good to excellent yields. Mechanistic studies, combining cyclic voltammetry and density functional theory calculations, support a radical-mediated hydrogen atom transfer mechanism driven by phthalimide-N-oxyl radicals. Importantly, the utility of the protocol extends beyond model substrates: it is successfully applied to the synthesis of pharmaceutically relevant compounds, including talopram and a key intermediate for a neuropeptide Y5 receptor antagonist. Overall, this work underscores the power of electrosynthesis in modern organic chemistry, merging green chemistry principles with synthetic efficiency.