Stable Intermediates Research Articles

Unveiling Phenoxazine's Unique Reversible Two-Electron Transfer Process and Stable Redox Intermediates for High-Performance Aqueous Zinc-ion Batteries.

The low specific capacity determined by the limited electron transfer of p-type cathode materials is the main obstruction to their application towards high-performance aqueous zinc-ion batteries (ZIBs). To overcome this challenge, boosting multi-electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p-type material, we unveil the unique reversible two-electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non-aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed-shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non-equivalent hybridized sp2-N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g-1 compared to other p-type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi-electron transfer phenoxazine moieties for high-performance aqueous ZIBs.

Ultrastable Anion Radicals in Ligand-Dimerized Frameworks for Self-Accumulated Electrochemiluminescence.

Electrochemiluminescence (ECL) is a light-emitting process that occurs via an annihilation reaction among energetic radical intermediates, whose stabilities determine the ECL efficiency. In this study, a ligand-dimerized metal-organic framework (MOF) with ultrastable anion radical is designed as an efficient nanoemitter for self-accumulated ECL. Due to the nonplanar structure of perylene diimide (PDI) derivate, two PDI ligands in the framework form a J-dimer unit with a vertical distance of ∼5.74 Å. In cathodic scanning, the ligand-dimerized MOF demonstrates three-step ECL emissions with a gradual increase in ECL intensity. Unlike the decrease in the PDI ligand, the self-accumulated ECL of the MOF was observed with 16.8-fold enhancement due to the excellent stability of radical intermediates in frameworks. Electron paramagnetic resonance demonstrated the ultrastability of free radicals in the designed frameworks, with 82.2% remaining even after one month of storage. Density functional theory calculations supported that PDI dimerization was energetically favorable upon successive electron injection. Moreover, the ECL wavelength is 610 nm, corresponding to the emission of excited dimers. The radical-stabilized reticular nanoemitters open up a new platform for decoding the fundamentals of self-accumulated ECL systems.

Rational Design of Cobalt Phthalocyanine (CoPc)‐Anchored TiO2 Nanorods for High‐Efficiency Selective Catalytic Oxidation

AbstractQuinclorac is important precursor for pharmaceutical, agricultural, and synthetic chemistry. The state‐of‐art synthesis of quinclorac via condensation, chlorination and oxidative hydrolysis often uses homogeneous catalysts and strong acid oxidant agents to promote the catalytic oxidation, which requires huge manpower input for the late‐stage purification process and is usually environmentally unfriendly. In this work, we successfully fabricated a stable cobalt phthalocyanine (CoPc) Co‐based composite (CoPc/TiO2) by anchoring CoPc on the surface of TiO2 nanorods for the selective oxidation of 3,7‐dichloro‐8‐dichloro methyl quinoline (3,7‐D‐8‐DMQ) into quinclorac. More impressively, CoPc/TiO2‐2.5 %‐Mn‐Br exhibits a high selectivity of 91.9 % for the catalytic oxidation of 3,7‐D‐8‐DMQ to quinclorac in acetic acid, with a quinclorac yield of 86.4 %, which is approximately 2.43 times higher than that of pristine CoPc‐Mn‐Br. The obtained heterogeneous catalytic system shows good reusability. Detailed mechanistic investigations reveal that the system works through a free radical mechanism via the formation of Co2+/Co3+ redox cycles. This work provides a new understanding for the stabilization of reaction intermediates and facilitates the designs of catalysts for selective catalytic oxidation.

Conformational Isomerization as a Process to Determine Selectivity over Reaction Pathways: Effect of Alkene Rotation in Chain Walking via Cis Alkene Intermediates.

In organic reactions, bond-forming and bond-cleaving processes are generally considered to be more important than other processes such as conformational isomerization. We report herein an example where a conformational isomerization process, propeller-like alkene rotation, is considered to determine the selectivity over the reaction pathways. The transition state with the highest energy barrier in some alkylpalladium isomerization (chain walking) events was theoretically indicated to correspond to alkene rotation, while transition states for bond-cleaving β-hydride elimination and bond-forming migratory insertion were not even observed. It was also suggested both theoretically and experimentally that the palladium chain walking over internal carbons in alkyl chains proceeds via cis alkene intermediates rather than thermodynamically more stable trans alkene intermediates, due to their relative difficulty to undergo alkene rotation.

Abstract 47: Stabilization of long CAR T cells is crucial for in vivo antitumor efficacy

Abstract Introduction: Genetically engineered T cells expressing chimeric antigen receptors (CARs) have shown substantial anti-tumor efficacy in hematological malignancies during recent years. As the field evolves to novel target epitopes, longer CAR structures are needed to reach membrane proximal epitopes for improved efficacy. Our approach to reach such epitopes is to have (non-functional) SIRPalpha based extracellular extension, spacer, to our CAR structure. We have shown, in this proof-of-concept study, that stability of the extracellular spacer of a CAR plays a pivotal role to improve in vivo anti-tumor efficacy. Various SIRPalpha-based CARs, FiCARs, targeting CD19 was studied for their function. Protein stability of the CD19 CAR structures were characterized and subsequently the killing efficacy of target cells and cytokine release in in vitro as well as in vivo anti-tumor efficacy was evaluated. Methods & Results: In vitro co-culture assays with primary CD19 CAR T and CD19 positive cancer cells had shown no significant differences between the different spacer containing FiCAR structures. A dose dependent killing efficacy was observed in all the tested structures with up to >90% killing of NALM6 and Raji cells. Comparable results for IL-2, IFN-gamma, TNF-alpha, IL-4, IL-13 and granzyme B response were seen in co-cultured assay. In the protein stability studies, modifications in the extracellular part of the CAR structure led to an increase in thermal stability (over 2 °C) and reduced/halted multimer formation. To study the FiCAR T cell function in an in vivo tumor model, NSG mice were injected i.v with Raji cells and few days later mice were injected i.v with FiCAR T cells. Anti-tumor efficacy and overall survival were studied at the end of the study (60 days), the enhanced stability of FiCAR T structure translated into improved anti-tumor efficacy and survival. Interestingly, none of the mice survived in the least stable structure, 40% survival with intermediate stability structures and over 70% survival was observed in most stable structures. Conclusion: A stabilized SIRPalpha-based CD19 FiCARs dramatically enhance anti-tumor efficacy and survival in Raji tumor model. The stabilization is critical for improved efficacy, especially in the in vivo setting. This data suggests that, in addition to the length of the CARs stability of the CAR structure appear to play a crucial role in the efficacy of the CAR T cells. The modifications presented here enhanced CD19-targeting CAR T cell efficacy. This approach requires further investigation to improve the efficacy of currently approved CAR T cells, especially CD19-CAR T cells. Citation Format: Henrik Paavilainen, Jan Koski, Veera Nikoskelainen, Manar Elmadani, Endrit Elbasani, Can Hekim, Emmi-Leena Ihantola, Virginie Kergourlay, Pirjo Vehmaan-kreula, Marie Nyman, Kiira Kalke, Markus Nurmi, Hector Monzo, Paivi Ojala, Anu Autio, Matti Korhonen, Anil Thotakura. Stabilization of long CAR T cells is crucial for in vivo antitumor efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 47.

Phase engineering of Fe2O3 nanocrystals for the direct oxidation of CH4 to HCOOH

The direct oxidation of methane (CH4) under mild conditions is a highly desirable technology to achieve the low-carbon and atom-economic production of high-value-added C1 oxygenates. However, the difficult activation of the CH bond of CH4 and the overoxidation of C1 oxygenates to carbon dioxide (CO2) are still the major bottlenecks. Herein, we systematically investigate the phase engineering of Fe2O3 in dependence on the performance of the direct oxidation of CH4. The cubic phase of Fe2O3 (Fe2O3-c) nanocrystals enables the direct oxidation of CH4 to HCOOH (DOMF) under mild aqueous conditions, and the HCOOH yield and selectivity could reach 6.315 mmol gcat−1 h−1 and 89.4%, which are 69.3 and 1.34 times higher than those of the hexagonal phase of Fe2O3 (Fe2O3-h) nanocrystals. Mechanism experiments indicate that Fe2O3-c nanocrystals can optimal CH4 adsorption behavior, favoring to the occurrence of the DOMF. In addition, in situ DRIFTS demonstrates that the DOMF is the radical reaction process that the activation of CH bond is caused by the ·OH radical. Subsequently, the unstable CH3OOH and stable CH3OH intermediates undergo further oxidation to form HCOOH. This work offers the phase engineering strategy to enhance the catalytic performance and reveal the reaction mechanism for the direct oxidation of CH4.

Role of Explicit Solvation in Computational Modeling of Chemical Reactions: Mechanism of Cu(I) Transfer Between Thiolate-Based Chelators in Water.

Solvation plays important roles in controlling the thermodynamic and kinetic aspects of chemical reactions. The conventional approaches to treat solvation via electronic structure methods are likely to become inadequate, when the reacting solutes have strong electrostatic and hydrogen bonding interactions with the solvent and undergo significant structural changes during the course of the reaction. In this article, we present evidence of such solvent and structural effects in the computational study of the Cu(I) transfer reaction between thiolate-based chelators dithiobutylamine (DTBA) and dithiotheritol (DTT) in water, inspired from biological copper trafficking phenomena. We propose a general solution to the problem by combining classical molecular dynamics (MD) simulations of the bulk system and static quantum chemistry calculations. The fluctuating solvation shell was estimated from MD, and energetics was assessed by averaging QM energies of a series of molecular clusters constructed from the MD snapshots. Applying this approach, we propose a reaction pathway with estimates of relative intermediate stabilities and barriers, which suggest the overall reaction to be reversible in nature and likely to go through both two and three coordinated intermediates, confirming previous studies of similar protein analogues. An interesting fact that emerged from our study was the strong indication that the rate-determining step is the deprotonation of initial thiol bound Cu(I) complex, without involving any Cu(I)-S bonds. The proposed method will lead to a better treatment of solvations, and these mechanistic insights will aid our understanding of biological copper(I) trafficking.

Mechanistic Insight into the Mechanical Unfolding of the Integral Membrane Diacylglycerol Kinase.

The essential forces stabilizing membrane proteins and governing their folding and unfolding are difficult to decipher. Single-molecule atomic force spectroscopy mechanically unfolds individual membrane proteins and quantifies their dynamics and energetics. However, it remains challenging to structurally assign unfolding intermediates precisely and to deduce dominant interactions between specific residues that facilitate either the localized stabilization of these intermediates or the global assembly of membrane proteins. Here, we performed force spectroscopy experiments and multiscale molecular dynamics simulations to study the unfolding pathway of diacylglycerol kinase (DGK), a small trimeric multispan transmembrane enzyme. The remarkable agreement between experiments and simulations allowed precise structural assignment and interaction analysis of unfolding intermediates, bypassing existing limitations on structural mapping, and thus provided mechanistic explanations for the formation of these states. DGK unfolding was found to proceed with structural segments varying in size that do not correlate with its secondary structure. We identified intermolecular side-chain packing interactions as one of the major contributions to the stability of unfolding intermediates. Mutagenesis creating packing defects induced a dramatic decrease in the mechano-stability of corresponding intermediates and also in the thermo-stability of DGK trimer, in good agreement with predictions from simulations. Hence, the molecular determinants of the mechano- and thermo-stability of a membrane protein can be identified at residue resolution. The accurate structural assignment established and microscopic mechanism revealed in this work may substantially expand the scope of single-molecule studies of membrane proteins.

In situ single-molecule investigations of the impacts of biochemical perturbations on conformational intermediates of monomeric α-synuclein.

α-Synuclein aggregation is a common trait in synucleinopathies, including Parkinson's disease. Being an unstructured protein, α-synuclein exists in several distinct conformational intermediates, contributing to both its function and pathogenesis. However, the regulation of these monomer conformations by biochemical factors and potential drugs has remained elusive. In this study, we devised an in situ single-molecule manipulation approach to pinpoint kinetically stable conformational intermediates of monomeric α-synuclein and explore the effects of various biochemical factors and drugs. We uncovered a partially folded conformation located in the non-amyloid-β component (NAC) region of monomeric α-synuclein, which is regulated by a preNAC region. This conformational intermediate is sensitive to biochemical perturbations and small-molecule drugs that influencing α-synuclein's aggregation tendency. Our findings reveal that this partially folded intermediate may play a role in α-synuclein aggregation, offering fresh perspectives for potential treatments aimed at the initial stage of higher-order α-synuclein aggregation. The single-molecule approach developed here can be broadly applied to the study of disease-related intrinsically disordered proteins.

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO2 Hydrogenation over a K−Fe/YZrOx Catalyst

AbstractA detailed operando DRIFTS study on the CO2 Fischer‐Tropsch reaction with K‐promoted Fe/YZrOx catalysts was performed to investigate the influence of this modification on the catalytic performance in the formation of lower olefins as well as higher hydrocarbons and to gain insights into mechanistic aspects. Catalytic testing revealed an enhanced formation of olefins and hydrocarbons by adding potassium to the catalysts, while spectroscopic studies revealed various stable adsorbates and intermediates such as monodentate carbonates, bicarbonates, formates, formyl, and methoxy on the surface of the K‐promoted Fe/YZrOx catalysts compared to the unpromoted one. Based on gas‐feed switching experiments and statistical analysis of literature IR data regarding Fe‐containing catalysts, it was found that carbonate species interacting with H2 are transformed to higher hydrocarbons and methane via formate and formyl formation, while bicarbonate species are decomposed accompanied by the formation of CO, which then further reacts to form formate or formyl and finally hydrocarbons.

Impact of the Methylene Bridge Substitution in Chelating NHC-Phosphine Mn(I) Catalyst for Ketone Hydrogenation.

Systematic modification of the chelating NHC-phosphine ligand (NHC = N-heterocyclic carbene) in highly efficient ketone hydrogenation Mn(I) catalyst fac-[(Ph2 PCH2 NHC)Mn(CO)3 Br] has been performed and the catalytic activity of the resulting complexes was evaluated using acetophenone as a benchmark substrate. While the variation of phosphine and NHC moieties led to inferior results than for a parent system, the incorporation of a phenyl substituent into the ligand methylene bridge improved catalytic performance by ca. 3 times providing maximal TON values in the range of 15000-20000. Mechanistic investigation combining experimental and computational studies allowed to rationalize this beneficial effect as an enhanced stabilization of reaction intermediates including anionic hydride species fac-[(Ph2 PC(Ph)NHC)Mn(CO)3 H]- playing a crucial role in the hydrogenation process. These results highlight the interest of such carbon bridge substitution strategy being rarely employed in the design of chemically non-innocent ligands.

Comprehensive exploration of the anaerobic biotransformation of polychlorinated biphenyls in Dehalococcoides mccartyi CG1: Kinetics, enantioselectivity, and isotope fractionation

Anaerobic microbial transformation is a key pathway in the natural attenuation of polychlorinated biphenyls (PCBs). Much less is known about the transformation behaviors induced by pure organohalide-respiring bacteria, especially kinetic isotope effects. Therefore, the kinetics, pathways, enantioselectivity, and carbon and chlorine isotope fractionation of PCBs transformation by Dehalococcoides mccartyi CG1 were comprehensively explored. The results indicated that the PCBs were mainly dechlorinated via removing their double-flanked meta-chlorine, with their first-order kinetic constants following the order of PCB132 > PCB174 > PCB85 > PCB183 > PCB138. However, PCBs occurred great loss of stoichiometric mass balance during microbial transformation, suggesting the generation of other non-dehalogenation products and/or stable intermediates. The preferential transformation of (−)-atropisomers and generation of (+)-atropisomers were observed during PCB132 and PCB174 biotransformation with the enantiomeric enrichment factors of −0.8609 ± 0.1077 and −0.4503 ± 0.1334 (first half incubation times)/−0.1888 ± 0.1354 (second half incubation times), respectively, whereas no enantioselectivity occurred during PCB183 biotransformation. More importantly, although there was no carbon and chlorine isotope fractionation occurring for studied substrates, the δ13C values of dechlorination products, including PCB47 (−28.15 ± 0.35‰ ∼ −27.77 ± 0.20‰), PCB91 (−36.36 ± 0.09‰ ∼ −34.71 ± 0.49‰), and PCB149 (−28.08 ± 0.26‰ ∼ −26.83 ± 0.10‰), were all significantly different from those of their corresponding substrates (PCB85: −30.81 ± 0.02‰ ∼ −30.22 ± 0.21‰, PCB132: −33.57 ± 0.15‰ ∼ −33.13 ± 0.14‰, and PCB174: −26.30 ± 0.09‰ ∼ −26.01 ± 0.07‰), which further supported the generation of other non-dehalogenation products and/or stable intermediates with enrichment or depletion of 13C. These findings provide deeper insights into the anaerobic microbial transformation behaviors of PCBs.

Pemanfaatan Batu Sungai Mappak Kabupaten Tana Toraja Dalam Campuran Laston Lapisan Antara

This research aims to find out how the aggregate characteristics of the Mappak River in Tana Toraja Regency can be used as a pavement material for asphalt mixtures. The method used is the conventional marshall method to obtain the properties of the mixture and marshall immersion to obtain residual marshall stability from the optimum asphalt content mixture. The results of the study indicated that the aggregate characteristics of the Mappak River stone in Tana Toraja Regency with an aggregate wear value of 21.6% met the specifications as a road pavement layer material for Mixed Laston Intermediate Layers with Optimum Asphalt Content of 6.20%, with the mixed properties of Laston Intermediate Layers, namely Density, Stability, flow, VIM, VMA, VFB and Marshall Quentient have met the Specifications of Bina Marga 2018. Through Marshall Immersion testing the Laston Intermediate Layers mixture with Optimum Asphalt Content of 6.20% obtained Remaining Marshall Stability of 95.07%, which means that it meets the Specifications Bina Marga 2018, namely at least 90%..

Unveiling Pre-Transmetalation Intermediates in Base-Free Suzuki-Miyaura Cross-Couplings: A Computational Study.

The pre-transmetalation intermediates are critically important in Suzuki-Miyaura cross-coupling (SMC) reactions and have become a hot spot of the current research. However, the pre-transmetalation intermediates under base-free conditions have not been clear. Herein, a comprehensive theoretical study is performed on the base-free Pd-catalyzed desulfonative SMC reaction. The fragile coordination feature and the acceleration role of the RuPhos chelate ligand are revealed. The hydrogen-bond complex between the Pd-F complex and aryl boronic acid is identified as an important pre-transmetalation intermediate, which increases the energy span to 32.5 kcal/mol. The controlling factor for the formation of the hydrogen-bond complexes is attributed to the electronegativities of halogen atoms in the metal halide complexes. What is more, other reported SMC reaction systems involving metal halide complexes and aryl boronic acids are reconsidered and suggest that the hydrogen-bond complexes widely exist as stable pre-transmetalation intermediates with influencing the catalytic activities. The earth-abundant Ni-catalyzed desulfonative SMC reaction is further designed and predicted to have a higher activity than the original Pd-catalyzed SMC reaction.

Site-selective protonation enables efficient carbon monoxide electroreduction to acetate

Electrosynthesis of acetate from CO offers the prospect of a low-carbon-intensity route to this valuable chemical––but only once sufficient selectivity, reaction rate and stability are realized. It is a high priority to achieve the protonation of the relevant intermediates in a controlled fashion, and to achieve this while suppressing the competing hydrogen evolution reaction (HER) and while steering multicarbon (C2+) products to a single valuable product––an example of which is acetate. Here we report interface engineering to achieve solid/liquid/gas triple-phase interface regulation, and we find that it leads to site-selective protonation of intermediates and the preferential stabilization of the ketene intermediates: this, we find, leads to improved selectivity and energy efficiency toward acetate. Once we further tune the catalyst composition and also optimize for interfacial water management, we achieve a cadmium-copper catalyst that shows an acetate Faradaic efficiency (FE) of 75% with ultralow HER (<0.2% H2 FE) at 150 mA cm−2. We develop a high-pressure membrane electrode assembly system to increase CO coverage by controlling gas reactant distribution and achieve 86% acetate FE simultaneous with an acetate full-cell energy efficiency (EE) of 32%, the highest energy efficiency reported in direct acetate electrosynthesis.

Dynamical Origin of Rebound versus Dissociation Selectivity during Fe-Oxo-Mediated C-H Functionalization Reactions.

The mechanism of catalytic C-H functionalization of alkanes by Fe-oxo complexes is often suggested to involve a hydrogen atom transfer (HAT) step with the formation of a radical-pair intermediate followed by diverging pathways for radical rebound, dissociation, or desaturation. Recently, we showed that in some Fe-oxo reactions, the radical pair is a nonstatistical-type intermediate and dynamic effects control rebound versus dissociation pathway selectivity. However, the effect of the solvent cage on the stability and lifetime of the radical-pair intermediate has never been analyzed. Moreover, because of the extreme complexity of motion that occurs during dynamics trajectories, the underlying physical origin of pathway selectivity has not yet been determined. For the reaction between [(TQA_Cl)FeIVO]+ and cyclohexane, here, we report explicit solvent trajectories and machine learning analysis on transition-state sampled features (e.g., vibrational, velocity, and geometric) that identified the transferring hydrogen atom kinetic energy as the most important factor controlling rebound versus nonrebound dynamics trajectories, which provides an explanation for our previously proposed dynamic matching effect in fast rebound trajectories that bypass the radical-pair intermediate. Manual control of the reaction trajectories confirmed the importance of this feature and provides a mechanism to enhance or diminish selectivity for the rebound pathway. This led to a general catalyst design principle and proof-of-principle catalyst design that showcases how to control rebound versus dissociation reaction pathway selectivity.

Stabilizing *CO2 Intermediates at the Acidic Interface using Molecularly Dispersed Cobalt Phthalocyanine as Catalysts for CO2 Reduction.

CO2 electroreduction (CO2 R) operating in acidic media circumvents the problems of carbonate formation and CO2 crossover in neutral/alkaline electrolyzers. Alkali cations have been universally recognized as indispensable components for acidic CO2 R, while they cause the inevitable issue of salt precipitation. It is therefore desirable to realize alkali-cation-free CO2 R in pure acid. However, without alkali cations, stabilizing *CO2 intermediates by catalyst itself at the acidic interface poses as a challenge. Herein, we first demonstrate that a carbon nanotube-supported molecularly dispersed cobalt phthalocyanine (CoPc@CNT) catalyst provides the Co single-atom active site with energetically localized d states to strengthen the adsorbate-surface interactions, which stabilizes *CO2 intermediates at the acidic interface (pH=1). As a result, we realize CO2 conversion to CO in pure acid with a faradaic efficiency of 60 % at pH=2 in flow cell. Furthermore, CO2 is successfully converted in cation exchanged membrane-based electrode assembly with a faradaic efficiency of 73 %. For CoPc@CNT, acidic conditions also promote the intrinsic activity of CO2 R compared to alkaline conditions, since the potential-limiting step, *CO2 to *COOH, is pH-dependent. This work provides a new understanding for the stabilization of reaction intermediates and facilitates the designs of catalysts and devices for acidic CO2 R.

Stabilizing *CO2 Intermediates at the Acidic Interface using Molecularly Dispersed Cobalt Phthalocyanine as Catalysts for CO2 Reduction

AbstractCO2 electroreduction (CO2R) operating in acidic media circumvents the problems of carbonate formation and CO2 crossover in neutral/alkaline electrolyzers. Alkali cations have been universally recognized as indispensable components for acidic CO2R, while they cause the inevitable issue of salt precipitation. It is therefore desirable to realize alkali‐cation‐free CO2R in pure acid. However, without alkali cations, stabilizing *CO2 intermediates by catalyst itself at the acidic interface poses as a challenge. Herein, we first demonstrate that a carbon nanotube‐supported molecularly dispersed cobalt phthalocyanine (CoPc@CNT) catalyst provides the Co single‐atom active site with energetically localized d states to strengthen the adsorbate‐surface interactions, which stabilizes *CO2 intermediates at the acidic interface (pH=1). As a result, we realize CO2 conversion to CO in pure acid with a faradaic efficiency of 60 % at pH=2 in flow cell. Furthermore, CO2 is successfully converted in cation exchanged membrane‐based electrode assembly with a faradaic efficiency of 73 %. For CoPc@CNT, acidic conditions also promote the intrinsic activity of CO2R compared to alkaline conditions, since the potential‐limiting step, *CO2 to *COOH, is pH‐dependent. This work provides a new understanding for the stabilization of reaction intermediates and facilitates the designs of catalysts and devices for acidic CO2R.

Cerium Oxide Catalyzed Disproportionation of Hydrogen Peroxide: A Closer Look at the Reaction Intermediate.

Cerium oxide nanoparticles (CNPs) have recently gained increasing interest as redox enzyme-mimetics to scavenge the intracellular excess of reactive oxygen species, including hydrogen peroxide (H2 O2 ). Despite the extensive exploration, there remains a notable discrepancy regarding the interpretation of observed redshift of UV-Visible spectroscopy due to H2 O2 addition and the catalase-mimicking mechanism of CNPs. To address this question, we investigated the reaction mechanism by taking a closer look at the reaction intermediate during the catalase mimicking reaction. In this study, we present evidence demonstrating that in aqueous solutions, H2 O2 adsorption at CNP surface triggers the formation of stable intermediates known as cerium-peroxo (Ce-O2 2- ) and/or cerium-hydroperoxo (Ce-OOH- ) complexes as resolved by Raman scattering and UV-Visible spectroscopy. Polymer coating presents steric hinderance for H2 O2 accessibility to the solid-liquid interface limiting further intermediate formation. We demonstrate in depth that the catalytic reactivity of CNPs in the H2 O2 disproportionation reaction increases with the Ce(III)-fraction and decreases in the presence of polymer coatings. The developed approach using UV-Visible spectroscopy for the characterization of the surface peroxide species can potentially serve as a foundation for determining the catalytic reactivity of CNPs in the disproportionation of H2 O2 .

Ruthenium catalyzed efficient hydroformylation regulated by thiazolinyl-based phosphine

A catalytic system comprised of Ru3(CO)12, thiazolinyl-based phosphine (L1), and HBF4 enables the efficient hydroformylation, which the tautomer L1b is more favorable for the occurrence of the reaction as well as the additive HBF4 is beneficial for the formation of ruthenium hydrogen active species. The formation and stabilization of the critical Ru-complex intermediates were verified by the DFT calculations. The hydroformylation proceeds with high chemical selectivity especially for the linear, internal and cyclic olefins (conversion up to 99 %, selectivity of aldehysdes up to 92 %).