Formation of Gas‐Phase Formate in Thermal Reactions of Carbon Dioxide with Diatomic Iron Hydride Anions

The hydrogenation of carbon dioxide involves the activation of the thermodynamically very stable molecule CO₂ and formation of a C−H bond. Herein, we report that HCO₂⁻ and CO can be formed in the thermal reaction of CO₂ with a diatomic metal hydride species, FeH⁻. The FeH⁻ anions were produced by laser ablation, and the reaction with CO₂ was analyzed by mass spectrometry and quantum‐chemical calculations. Gas‐phase HCO₂⁻ was observed directly as a product, and its formation was predicted to proceed by facile hydride transfer. The mechanism of CO₂ hydrogenation in this gas‐phase study parallels similar behavior of a condensed‐phase iron catalyst.     

Thermal Methane Activation by La6O10− Cluster Anions

The first example of a metal oxide cluster anion, La₆O₁₀^? that can activate methane under ambient conditions is reported. This reaction is facilitated by the oxygen‐centered radical (O^??) and follows the hydrogen atom transfer mechanism. The La₆O₁₀^? has a high vertical electron detachment energy (VDE=4.06 eV) and a high symmetry (C_4v).     

Selective Activation of the C−H Bond in Methane by Single Platinum Atomic Anions

Mass spectrometric analysis of the anionic products of interaction between platinum atomic anions, Pt^?, and methane, CH₄ and CD₄, in a collision cell shows the preferred generation of [PtCH₄]^? and [PtCD₄]^? complexes and a low tendency toward dehydrogenation. [PtCH₄]^? is shown to be H?Pt?CH₃^? by a synergy between anion photoelectron spectroscopy and quantum chemical calculations, implying the rupture of a single C?H bond. The calculated reaction pathway accounts for the observed selective activation of methane by Pt^?. This study presents the first example of methane activation by a single atomic anion.     

One‐Step Reforming of CO2 and CH4 into High‐Value Liquid Chemicals and Fuels at Room Temperature by Plasma‐Driven Catalysis

The conversion of CO₂ with CH₄ into liquid fuels and chemicals in a single‐step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one‐step process from CO₂ and CH₄ at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH₄ and CO₂ is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.     

Thermal Methane Conversion to Formaldehyde Promoted by Single Platinum Atoms in PtAl2O4− Cluster Anions

Identification and mechanistic study of thermal methane conversion mediated by gas‐phase species is important for finding potentially useful routes for direct methane transformation under mild conditions. Negatively charged oxide species are usually inert with methane. This work reports an unexpected result that the bi‐metallic oxide cluster anions PtAl₂O₄^? can transform methane into a stable organic compound, formaldehyde, with high selectivity. The clusters are prepared by laser ablation and reacted with CH₄ in an ion trap reactor. The reaction is characterized by mass spectrometry and density functional theory calculations. It is found that platinum rather than oxygen activates CH₄ at the beginning of the reaction. The Al₂O₄^? moiety serves as the support of Pt atom and plays important roles in the late stage of the reaction. A new mechanism for selective methane conversion is provided and new insights into the surface chemistry of single Pt atoms may be obtained from this study.     

Low‐Temperature Hydrogenation of Carbon Dioxide to Methanol with a Homogeneous Cobalt Catalyst

Herein we describe the first homogeneous non‐noble metal catalyst for the hydrogenation of CO₂ to methanol. The catalyst is formed in situ from [Co(acac)₃], Triphos, and HNTf₂ and enables the reaction to be performed at 100 °C without a decrease in activity. Kinetic studies suggest an inner‐sphere mechanism, and in situ NMR and MS experiments reveal the formation of the active catalyst through slow removal of the acetylacetonate ligands.     

Stereospecific Decarboxylative Nazarov Cyclization Mediated by Carbon Dioxide for the Preparation of Highly Substituted 2‐Cyclopentenones

Highly substituted 2‐cyclopentenones were stereospecifically and regioselectively constructed with high catalytic efficiency through Lewis‐acid catalyzed decarboxylative Nazarov cyclization of the cyclic carbonate derivative, which is prepared by reacting the propargyl alcohol with carbon dioxide in the presence of a silver catalyst. The stereochemistry of the 2‐cyclopentenone is strictly controlled by the geometry of the alkene in the starting material. This method is applicable for various substrates.     

Activation of Methane Promoted by Adsorption of CO on Mo2C2− Cluster Anions

Atomic clusters are being actively studied for activation of methane, the most stable alkane molecule. While many cluster cations are very reactive with methane, the cluster anions are usually not very reactive, particularly for noble metal free anions. This study reports that the reactivity of molybdenum carbide cluster anions with methane can be much enhanced by adsorption of CO. The Mo₂C₂^? is inert with CH₄ while the CO addition product Mo₂C₃O^? brings about dehydrogenation of CH₄ under thermal collision conditions. The cluster structures and reactions are characterized by mass spectrometry, photoelectron spectroscopy, and quantum chemistry calculations, which demonstrate that the Mo₂C₃O^? isomer with dissociated CO is reactive but the one with non‐dissociated CO is unreactive. The enhancement of cluster reactivity promoted by CO adsorption in this study is compared with those of reported systems of a few carbonyl complexes.     

Catalytic CO Oxidation by O2 Mediated by Noble‐Metal‐Free Cluster Anions Cu2VO3–5−

Catalytic CO oxidation by molecular O₂ is an important model reaction in both the condensed phase and gas‐phase studies. Available gas‐phase studies indicate that noble metal is indispensable in catalytic CO oxidation by O₂ under thermal collision conditions. Herein, we identified the first example of noble‐metal‐free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu₂VO_3–5^? for CO oxidation by O₂. The reactions were characterized by mass spectrometry, photoelectron spectroscopy, and density functional calculations. The dynamic nature of the Cu?Cu unit in terms of the electron storage and release is the driving force to promote CO oxidation and O₂ activation during the catalysis.     

Tailor‐made Molecular Cobalt Catalyst System for the Selective Transformation of Carbon Dioxide to Dialkoxymethane Ethers

Herein a non‐precious transition‐metal catalyst system for the selective synthesis of dialkoxymethane ethers from carbon dioxide and molecular hydrogen is presented. The development of a tailored catalyst system based on cobalt salts in combination with selected Triphos ligands and acidic co‐catalysts enabled a synthetic pathway, avoiding the oxidation of methanol to attain the formaldehyde level of the central CH₂ unit. This unprecedented productivity based on the molecular cobalt catalyst is the first example of a non‐precious transition‐metal system for this transformation utilizing renewable carbon dioxide sources.     

Formation of Acetylene in the Reaction of Methane with Iron Carbide Cluster Anions FeC3− under High‐Temperature Conditions

The underlying mechanism for non‐oxidative methane aromatization remains controversial owing to the lack of experimental evidence for the formation of the first C?C bond. For the first time, the elementary reaction of methane with atomic clusters (FeC₃^?) under high‐temperature conditions to produce C?C coupling products has been characterized by mass spectrometry. With the elevation of temperature from 300 K to 610 K, the production of acetylene, the important intermediate proposed in a monofunctional mechanism of methane aromatization, was significantly enhanced, which can be well‐rationalized by quantum chemistry calculations. This study narrows the gap between gas‐phase and condensed‐phase studies on methane conversion and suggests that the monofunctional mechanism probably operates in non‐oxidative methane aromatization.