NHC‐Coordinated Diphosphene‐Stabilized Gold(I) Hydride and Its Reversible Conversion to Gold(I) Formate with CO2

An NHC‐coordinated diphosphene is employed as ligand for the synthesis of a hydrocarbon‐soluble monomeric Au^I hydride, which readily adds CO₂ at room temperature yielding the corresponding Au^I formate. The reversible reaction can be expedited by the addition of NHC, which induces β‐hydride shift and the removal of CO₂ from equilibrium through the formation of an NHC‐CO₂ adduct. The Au^I formate is alternatively formed by dehydrogenative coupling of the Au^I hydride with formic acid (HCO₂H), thus in total establishing a reaction sequence for the Au^I hydride mediated dehydrogenation of HCO₂H as chemical hydrogen storage material.     

Self‐Cleaning Catalyst Electrodes for Stabilized CO2 Reduction to Hydrocarbons

A surface‐restructuring strategy is presented that involves self‐cleaning Cu catalyst electrodes with unprecedented catalytic stability toward CO₂ reduction. Under the working conditions, the Pd atoms pre‐deposited on Cu surface induce continuous morphological and compositional restructuring of the Cu surface, which constantly refreshes the catalyst surface and thus maintains the catalytic properties for CO₂ reduction to hydrocarbons. The Pd‐decorated Cu electrode can catalyze CO₂ reduction with relatively stable selectivity and current density for up to 16 h, which is one of the best catalytic durability performances among all Cu electrocatalysts for effective CO₂ conversion to hydrocarbons. The generality of this approach of utilizing foreign metal atoms to induce surface restructuring toward stabilizing Cu catalyst electrodes against deactivation by carbonaceous species accumulation in CO₂ reduction is further demonstrated by replacing Pd with Rh.     

Copper‐Bismuth Bimetallic Microspheres for Selective Electrocatalytic Reduction of CO2 to Formate

Electrocatalytic carbon dioxide reduction holds great promise for reducing the atmospheric CO₂ level and alleviating the energy crisis. High‐performance electrocatalysts are often required in order to lower the high overpotential and expedite the sluggish reaction kinetics of CO₂ electroreduction. Copper is a promising candidate metal. However, it usually suffers from the issues of poor stability and low product selectivity. In this work, bimetallic Cu‐Bi is obtained by reducing the microspherical copper bismuthate (CuBi₂O₄) for selectively catalyzing the CO₂ reduction to formate (HCOO^–). The bimetallic Cu‐Bi electrocatalyst exhibits high activity and selectivity with the Faradic efficiency over 90% in a wide potential window. A maximum Faradaic efficiency of ~95% is obtained at –0.93 V versus reversible hydrogen electrode. Furthermore, the catalyst shows high stability over 6 h with Faradaic efficiency of ~95%. This study provides an important clue in designing new functional materials for CO₂ electroreduction with high activity and selectivity.     

Catholyte‐Free Electrocatalytic CO2 Reduction to Formate

Electrochemical reduction of carbon dioxide (CO₂) into value‐added chemicals is a promising strategy to reduce CO₂ emission and mitigate climate change. One of the most serious problems in electrocatalytic CO₂ reduction (CO₂R) is the low solubility of CO₂ in an aqueous electrolyte, which significantly limits the cathodic reaction rate. This paper proposes a facile method of catholyte‐free electrocatalytic CO₂ reduction to avoid the solubility limitation using commercial tin nanoparticles as a cathode catalyst. Interestingly, as the reaction temperature rises from 303 K to 363 K, the partial current density (PCD) of formate improves more than two times with 52.9 mA cm^?2, despite the decrease in CO₂ solubility. Furthermore, a significantly high formate concentration of 41.5 g L^?1 is obtained as a one‐path product at 343 K with high PCD (51.7 mA cm^?2) and high Faradaic efficiency (93.3 %) via continuous operation in a full flow cell at a low cell voltage of 2.2 V.     

Aqueous CO2 Reduction with High Efficiency Using α‐Co(OH)2‐Supported Atomic Ir Electrocatalysts

Electrochemical reduction of CO₂ into energy‐dense chemical feedstock and fuels provides an attractive pathway to sustainable energy storage and artificial carbon cycle. Herein, we report the first work to use atomic Ir electrocatalyst for CO₂ reduction. By using α‐Co(OH)₂ as the support, the faradaic efficiency of CO could reach 97.6 % with a turnover frequency (TOF) of 38290 h^?1 in aqueous electrolyte, which is the highest TOF up to date. The electrochemical active area is 23.4‐times higher than Ir nanoparticles (2 nm), which is highly conductive and favors electron transfer from CO₂ to its radical anion (CO₂^.?). Moreover, the more efficient stabilization of CO₂^.? intermediate and easy charge transfer makes the atomic Ir electrocatalyst facilitate CO production. Hence, α‐Co(OH)₂‐supported atomic Ir electrocatalysts show enhanced CO₂ activity and stability.     

Isolated Square‐Planar Copper Center in Boron Imidazolate Nanocages for Photocatalytic Reduction of CO2 to CO

Photocatalytic reduction of CO₂ to value‐added fuel has been considered to be a promising strategy to reduce global warming and shortage of energy. Rational design and synthesis of catalysts to maximumly expose the active sites is the key to activate CO₂ molecules and determine the reaction selectivity. Herein, we synthesize a well‐defined copper‐based boron imidazolate cage (BIF‐29) with six exposed mononuclear copper centers for the photocatalytic reduction of CO₂. Theoretical calculations show a single Cu site including weak coordinated water delivers a new state in the conduction band near the Fermi level and stabilizes the *COOH intermediate. Steady‐state and time‐resolved fluorescence spectra show these Cu sites promote the separation of electron–hole pairs and electron transfer. As a result, the cage achieves solar‐driven reduction of CO₂ to CO with an evolution rate of 3334 μmol g^?1 h^?1 and a high selectivity of 82.6 %.     

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.     

Halogen-Incorporated Sn Catalysts for Selective Electrochemical CO2 Reduction to Formate

Electrochemically reducing CO₂ to valuable fuels or feedstocks is recognized as a promising strategy to simultaneously tackle the crises of fossil fuel shortage and carbon emission. Sn-based catalysts have been widely studied for electrochemical CO₂ reduction reaction (CO₂RR) to make formic acid/formate, which unfortunately still suffer from low activity, selectivity and stability. In this work, halogen (F, Cl, Br or I) was introduced into the Sn catalyst by a facile hydrolysis method. The presence of halogen was confirmed by a collection of ex situ and in situ characterizations, which rendered a more positive valence state of Sn in halogen-incorporated Sn catalyst as compared to unmodified Sn under cathodic potentials in CO₂RR and therefore tuned the adsorption strength of the key intermediate (*OCHO) toward formate formation. As a result, the halogen-incorporated Sn catalyst exhibited greatly enhanced catalytic performance in electrochemical CO₂RR to produce formate.     

Copper‐Catalyzed 1,2‐Methoxy Methoxycarbonylation of Alkenes with Methyl Formate

Reported here is a copper‐catalyzed 1,2‐methoxy methoxycarbonylation of alkenes by an unprecedented use of methyl formate as a source of both the methoxy and the methoxycarbonyl groups. This reaction transforms styrene and its derivatives into value‐added β‐methoxy alkanoates and cinnamates, as well as medicinally important five‐membered heterocycles, such as functionalized tetrahydrofurans, γ‐lactones, and pyrrolidines. A ternary β‐diketiminato‐Cu^I‐styrene complex, fully characterized by NMR spectroscopy and X‐ray crystallographic analysis, is capable of catalyzing the same transformation. These findings suggest that pre‐coordination of electron‐rich alkenes to copper might play an important role in accelerating the addition of nucleophilic radicals to electron‐rich alkenes, and could have general implications in the design of novel radical‐based transformations.     

Hydrogenation of CO2 to Formate with H2: Transition Metal Free Catalyst Based on a Lewis Pair

Hydrogenation of CO₂ to formate with H₂ in the absence of transition metal is a long‐standing challenge in catalysis. The reactions between tris(pentafluorophenyl)borane (BCF) and K₂CO₃ (or KHCO₃) are found to form a Lewis pair (K₂[(BCF)₂?CO₃]) which can react with both H₂ and CO₂ to produce formate. Based on these stoichiometric reactions, the first catalytic hydrogenation process of CO₂ to formate using transition metal free catalyst (BCF/M₂CO₃, M=Na, K, and Cs) is reported. The highest TON value of this catalytic process is up to 3941. Further research revealed the reaction mechanism in which the Lewis pair enables the splitting of H₂ and the insertion of CO₂ into the B?H bond.     

Gold‐catalyzed [4+2] Annulations of Dienes with Nitrosoarenes as 4 π Donors: Nitroso‐Povarov Reactions

This work reports the first success of the nitroso‐Povarov reaction, involving gold‐catalyzed [4+2] annulations of nitrsoarenes with substituted cyclopentadienes. In this catalytic sequence, nitrosoarenes presumably attack gold‐π‐dienes by a 1,4‐addition pathway, generating allylgold nitrosonium intermediates to complete an intramolecular cyclization. Acyclic dienes are also applicable substrates, and affording oxidative nitroso‐Povarov products.