Špela Kunstelj

Electrocatalytic hydrogenation (e -H) provides a sustainable route for converting unsaturated organic substrates under mild conditions using renewable electricity as the driving force. Here, we report an MOF-derived cobalt catalyst for the e -H of acetone and pyridine. A new two-dimensional cobalt metal–organic framework, Co-L0-NS, composed of Co(II) nodes and polyaromatic carboxylate linkers, was synthesized as nanosheets and used as a precursor to generate the active catalyst under cathodic bias. Electrochemical pretreatment induces controlled framework reconstruction to form MD-Cat, a highly dispersed, structurally disordered, Co(OH)2-rich nanocluster material. MD-Cat catalyzes the e -H of acetone to isopropanol with nearly quantitative Faradaic efficiency at optimized potentials and promotes pyridine hydrogenation to piperidine with up to 50% Faradaic efficiency. Comparative studies with electrodeposited cobalt, commercial cobalt nanoparticles, and bulk Co(OH)2 show that the MOF-derived catalyst exhibits superior current densities and product selectivity, which we attribute to its nanoscale morphology and hydroxylated cobalt environment. In situ Co K-edge XAS, XPS, PXRD, ATR-SEIRAS, and STEM analyses indicate that Co remains predominantly in the +2 oxidation state during catalysis while undergoing structural reorganization. Tafel analysis supports a PCET-type mechanism for acetone hydrogenation; while DFT calculations suggest that the Co/Co(OH)2 interface suppresses HER by weakening H* binding while preserving organic-substrate activation. These results highlight MOF-templated electrochemical reconstruction as a promising approach for designing selective e -H catalysts, not only by increasing catalyst accessibility through nanostructuring but also by enabling the formation of unique catalytic motifs that would otherwise be difficult to access using traditional methods.

Fe₄S₄ clusters play essential roles in nature, classically in electron transport but increasingly in newly discovered reactivity or catalysis. These roles have spurred interest in developing synthetic Fe₄S₄ systems and while several molecular and material systems built from Fe₄S₄ clusters have been developed, comparatively few examples of synthetic Fe₄S₄ cluster-based catalysts exist. Herein, we present the use of an Fe₄S₄-based coordination polymer as a catalyst for the direct and selective electroreduction of CO₂ to CO. Computational studies suggest that the reaction proceeds through CO₂ binding to a reduced Fe₄S₄ cluster, followed by a series of protonation, reduction, and H₂O loss steps to yield a CO-bound cluster that can finally exchange with CO₂ to restart the catalytic cycle. CO bound clusters are predicted to be thermodynamically stable, suggesting that carbonyl species might be off-cycle intermediates. Mechanistic CV studies as well as in situ studies by IR spectroscopy provide evidence for carbonyl-ligated clusters, supporting these compounds as unusual examples of small molecule binding to Fe₄S₄ clusters. This work establishes Fe₄S₄ cluster-based coordination polymers as direct electrocatalysts for CO₂ reduction and provides mechanistic insights into how these species mediate catalytic conversions of small molecules.

Fe₄S₄ clusters play essential roles in nature, classically in electron transport but increasingly in newly discovered reactivity or catalysis. These roles have spurred interest in developing synthetic Fe4S4 systems and while several molecular and material systems based on Fe₄S₄ clusters have been developed, comparatively few examples of synthetic Fe₄S₄ cluster-based catalysts exist. Herein, we present the use of an Fe₄S₄-based coordination polymer as a catalyst for the direct and selective electroreduction of CO2 to CO. Computational studies suggest that the reaction proceeds through CO2 binding to a reduced Fe4S4 cluster, followed by a series of protonation, reduction, and H2O loss steps to yield a CO-bound cluster that can finally exchange with CO2 to restart the catalytic cycle. CO bound clusters are predicted to be thermodynamically stable, suggesting that carbonyl species might be off-cycle intermediates. Mechanistic CV studies as well as in situ studies by IR spectroscopy provide evidence for carbonyl-ligated clusters, supporting these compounds as unusual examples of small molecule binding to Fe4S4 clusters. This work establishes Fe4S4 cluster-based coordination polymers as direct electrocatalysts for CO2 reduction and provides mechanistic insights into how these clusters mediate catalytic conversions of small molecules.

Aggregates of misfolded α-synuclein proteins are key markers of Parkinson’s disease. The protein α-synuclein (aSyn) is an intrinsically disordered protein (IDP) and therefore lacks a single stable 3D structure, instead sampling multiple conformations in solution. It is primarily located in presynaptic terminals and is thought to help regulate synaptic vesicle trafficking and neurotransmitter release. ASyn proteins have three domains: an N-terminal domain, a hydrophobic non-amyloid-β component (NAC) core implicated in aggregation, and a proline-rich C-terminal domain. Asyn proteins with truncated C-terminal domains are known to be prone to aggregation and suggest that understanding domain–domain interactions in aSyn monomers could help elucidate the role of the flanking domains in modulating protein structure. To this end, we used Gaussian accelerated molecular dynamics (GAMD) to simulate wild-type (WT), N-terminal truncated (ΔN), C-terminal truncated (ΔC), and isolated NAC domain (isoNAC) aSyn protein variants. Using clustering and contact analysis, we found that removal of the N-terminal domain led to increased contacts between NAC and C-terminal domains and the formation of inter-domain β-sheets. Removal of either flanking domain also resulted in increased compactness of every domain. We also found that the contacts between flanking domains in the WT protein result in an electrostatic potential (ESP) that may lead to favorable interactions with anionic lipid membranes. Removal of the C-terminal domain disrupts the ESP in a way that could result in over-stabilized protein–membrane interactions. These results suggest that cooperation between the flanking domains may modulate the protein’s structure in a way that helps maintain elongation and creates an ESP that may aid favorable interactions with the membrane.

Electrochemical hydrogenation (e-H) of organic substrates represents a key transformation for advancing industrial electrification and sustainable chemical manufacturing. Here, we represent e-H of acetone and pyridine by cobalt nanoparticles derived from a Co-based MOF. A novel two-dimensional cobalt metal–organic framework, Co-L0-NS, featuring a kgd-type layered topology with Co(II) paddlewheel nodes and polyaromatic linkers, has been synthe-sized and structurally characterized. Electrochemical reduction of Co-L0-NS induces controlled framework recon-struction, producing highly dispersed cobalt nanoparticles that efficiently catalyze the e-H of acetone to isopropanol and show moderate activity toward pyridine reduction to piperidine. In contrast, electrodeposition from aqueous Co²⁺ precursors forms larger, more crystalline metallic Co particles. Spectroscopic and electrochemical analyses, sup-ported by Tafel modeling, indicate a proton-coupled electron-transfer (PCET) mechanism with a rate-determining step exhibiting a Tafel slope of ~150 mV dec⁻¹. These findings highlight how structural features of the parent MOF—open Co sites, two-dimensional connectivity, and redox flexibility—govern nanoparticle formation and catalytic be-havior, providing design principles for MOF-derived cobalt electrocatalysts.

The (non)-Kolbe oxidation of valeric acid, sourced from a hydrolysis product of cellulose, provides a sustainable synthetic route to access value-added products, such as butene. An essential mechanistic step preceding product formation involves the oxidative and decarboxylative cleavage of a C-C bond. Yet, the role of the electrode surface in mediating this oxidative step remains an open question: the electron transfer can occur either via an inner-sphere or outer-sphere mechanism. Here, we report the electrochemical, in situ spectroscopic, computational, and reactivity studies of RuO2-mediated oxidative decarboxylation of valeric acid to butene in aqueous electrolytes. We find that carboxylates bind to RuO2 anode surfaces at potential values where decarboxylation products are observed. Our results are consistent with a reaction scheme where the competitive and catalytic oxygen evolution reaction (OER) is impeded by these bound carboxylate species while these species are inert toward butene formation. Our results implicate an outer-sphere electron transfer mechanism for decarboxylation where the surface chemistry of the RuO2 electrode serves to enable higher non-Kolbe reaction selectivity by suppressing the parasitic OER. Our findings delineate interfacial design principles for selective electrochemical systems that utilize water as the ultimate oxidant for sustainable decarboxylation.

Iron-sulfur clusters play essential roles in biological systems, and thus synthetic [Fe₄S₄] clusters have been an area of active research. Recent studies have demonstrated that soluble [Fe₄S₄] clusters can serve as net H atom transfer mediators, improving the activity and selectivity of a homogeneous Mn CO₂ reduction catalyst. Here, we demonstrate that incorporating these [Fe₄S₄] clusters into a coordination polymer enables heterogeneous H atom transfer from an electrode surface to a Mn complex dissolved in solution. A previously reported solution-processable Fe₄S₄-based coordination polymer was successfully deposited on the surfaces of different electrodes. The coated electrodes serve as H atom transfer mediators to a soluble Mn CO₂ reduction catalyst displaying good product selectivity for formic acid. Furthermore, these electrodes are recyclable with a minimal decrease in activity after multiple catalytic cycles. The heterogenization of the mediator also enables the characterization of solution-phase and electrode surface species separately. Surface enhanced infrared absorption spectroscopy (SEIRAS) reveals spectroscopic signatures for an in situ generated active Mn-H species, providing a more complete mechanistic picture for this system. The active species, reaction mechanism, and the protonation sites on the [Fe₄S₄] clusters were further confirmed by density functional theory calculations. The observed H atom transfer reactivity of these coordination polymer-coated electrodes motivates additional applications of this composite material in reductive H atom transfer electrocatalysis.