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

Driving dimethyl carbonate synthesis from CO2 and methanol and production of acetylene simultaneously using CaC2

The synthesis of dimethyl carbonate (DMC) from CO2 and methanol is a very interesting reaction, but is thermodynamically limited. In this work, CaC2 was used to consume the water produced in the reaction to shift the reaction equilibrium, and C2H2 was produced at the same time. This is the first work on the combination of driving a thermodynamically unfavorable reaction and producing C2H2 using CaC2.

CO2-based hydrogen storage: CO2 hydrogenation to formic acid, formaldehyde and methanol

The storage of hydrogen via hydrogenation of CO2 to small organic molecules can be attractive for mobile applications. In this article, the state of the art regarding hydrogen storage in Methanol, Formic Acid as well as Formaldehyde and derivates based on CO2 hydrogenation is summarized. The reverse reaction, the release of hydrogen from these molecules is also crucial and described in the articles together with possible concepts for the use of hydrogen storage by CO2 hydrogenation.

Ethanol-mediated N-formylation of amines with CO2/H2 over cobalt catalysts

A cobalt-based system was developed for the selective formylation of amines with CO₂/H₂ using ethanol as the solvent.

Catalytic (de)hydrogenation promoted by non-precious metals – Co, Fe and Mn: recent advances in an emerging field

This review is aimed at introducing the remarkable progress made in the last three years in the development of base metal catalysts for hydrogenations and dehydrogenative transformations.

Hydrogenation of silyl formates: sustainable production of silanol and methanol from hydrosilane and carbon dioxide

Simultaneous production of methanol and silanols was achieved by hydrogenation of silyl formates readily obtained from silanes and CO₂.

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

CO₂ conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO₂ utilization as a measure for global CO₂ mitigation. Whereas the latter focuses on reducing the end-of-pipe problem "CO₂ emissions" from todays' industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO₂-based chemistry does not depend primarily on the absolute amount of CO₂ emissions that can be remediated by a single technology. Rather, CO₂-based chemistry is stimulated by the significance of the relative improvement in carbon balance and other critical factors defining the environmental impact of chemical production in all relevant sectors in accord with the principles of green chemistry.

Formates for green catalytic reductions via CO2 hydrogenation, mediated by magnetically recoverable catalysts

Precious metal catalyst has been prepared by conventional wet impregnation method followed by precipitation and reduction with hydrogen finally passivated with water in air. The magnetically recoverable catalyst has been prepared starting from a stoichiometric Fe3O4 and ZrO2–Fe3O4 as supports prepared following a sequential precipitation procedure. Precious metal catalysts supported on carbon, alumina, magnetite and zirconia-magnetite nanocomposite has been used in the reduction of nitrobenzenes and acetophenone by using sodium and potassium formate as reducing agent in the presence and in absence of an aqueous phase. In addition, the same catalysts has been tested in CO2 and NaHCO3 hydrogenation, for verifying their potentiality in the CO2 as hydrogen carrier for hydrogenation processes.

A Bimetallic Nickel-Gallium Complex Catalyzes CO2 Hydrogenation via the Intermediacy of an Anionic d10 Nickel Hydride

Large-scale CO₂ hydrogenation could offer a renewable stream of industrially important C₁ chemicals while reducing CO₂ emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO₂ to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h^-1), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d¹⁰ Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.

Cobalt-catalysed reductive C-H alkylation of indoles using carboxylic acids and molecular hydrogen

The direct CH-alkylation of indoles using carboxylic acids is presented for the first time. The catalytic system based on the combination of Co(acac)3 and 1,1,1-tris(diphenylphosphinomethyl)-ethane (Triphos, L1), in the presence of Al(OTf)3 as co-catalyst, is able to perform the reductive alkylation of 2-methyl-1H-indole with a wide range of carboxylic acids. The utility of the protocol was further demonstrated through the C3 alkylation of several substituted indole derivatives using acetic, phenylacetic or diphenylacetic acids. In addition, a careful selection of the reaction conditions allowed to perform the selective C3 alkenylation of some indole derivatives. Moreover, the alkenylation of C2 position of 3-methyl-1H-indole was also possible. Control experiments indicate that the aldehyde, in situ formed from the carboxylic acid hydrogenation, plays a central role in the overall process. This new protocol enables the direct functionalization of indoles with readily available and stable carboxylic acids using a non-precious metal based catalyst and hydrogen as reductant.

Challenges in the Greener Production of Formates/Formic Acid, Methanol, and DME by Heterogeneously Catalyzed CO2 Hydrogenation Processes

The recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO₂ to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO₂ capture and green routes to produce H₂. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO₂ valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions.

Unprecedented selective homogeneous cobalt-catalysed reductive alkoxylation of cyclic imides under mild conditions

The first general and efficient non-noble metal-catalysed reductive C2-alkoxylation of cyclic imides (phthalimides and succinimides) is presented. Crucial for the success is the use of [Co(BF₄)₂·6H₂O/triphos (L1)] combination and no external additives are required.

The first general and efficient non-noble metal-catalysed reductive C2-alkoxylation of cyclic imides (phthalimides and succinimides) is presented. Crucial for the success is the use of [Co(BF₄)₂·6H₂O/triphos (L1)] combination and no external additives are required. Using the optimal cobalt-system, the hydrogenation of the aromatic ring of the parent phthalimide is avoided and only one of the carbonyl groups is selectively functionalized. The resulting products, N- and aryl-ring substituted 3-alkoxy-2,3-dihydro-1H-isoindolin-1-one and N-substituted 3-alkoxy-pyrrolidin-2-one derivatives, are prepared under mild conditions in good to excellent isolated yields. Intramolecular reductive couplings can also be performed affording tricyclic compounds in a one-step process. The present protocol opens the way to the development of new base-metal processes for the straightforward synthesis of functionalized N-heterocyclic compounds of pharmaceutical and biological interest.

Highly productive CO2 hydrogenation to methanol – a tandem catalytic approach via amide intermediates

Amines to an end – homogeneous ruthenium catalysts based on mixed donor P–N ligands with a range of amine auxiliaries are highly productive for CO₂ reduction to methanol, the nature of this amine having a profound effect on performance.

Spectroscopic and reactivity differences in metal complexes derived from sulfur containing Triphos homologs

Spectroscopic, computational, and reactivity studies shed light on the different coordination behavior of sulfur containing Triphos derived complexes.