Catalytic Utilization of Carbon Dioxide as Renewable C1 Resource

  Snowman Urheberrecht: ITMC RWTH  

In the last two decades the utilization of renewable resources as chemical building block, solvent, or additive has emerged as important research area for the development of sustainable chemical processes. Carbon dioxide (our cold, stable, and generous SNOWMAN), is an important, but challenging renewable C1 resource, which is already used as raw material for the production of industrial chemicals in certain cases and intensively researched for novel transformations.


K. Beydoun, T. vom Stein, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 2013, 52, 9554. LINK
K. Beydoun, G. Ghattas, K. Thenert, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 2014, 53, 11010. LINK
K. Beydoun, K. Thenert, E. S. Streng, S. Brosinski, W. Leitner, J. Klankermayer, ChemCatChem 2016, 8, 135. LINK

1) N-Methylation of amines using CO2 and H2

Traditional pathways for N-methylation include alkylation with methyl iodide, orthoesters, or dimethyl carbonate or reductive alkylation such as the Eschweiler-Clark method using formaldehyde and formic acid as C1 source. A CO2-based route has the potential to be significantly more environmentally friendly and opens the possibility for new or complementary selectivities. Our group has disclosed the homogenously catalyzed direct N-methylation of anilines using CO2 and H2 as the only sources for the construction of the methyl group. The starting point for the investigation was the well-established triphos-based ruthenium system, which provides excellent homogeneous catalysts for the hydrogenation of amides, esters, and carboxylic acids.

  Ruthenium catalyzed direct N-methylation Urheberrecht: ITMC RWTH  

The new N-methylation method was also used on structurally diverse and readily accessible imines with CO2 and H2 that provides an effective synthesis of unsymmetrical tertiary N-methyl amines. Exploiting the chemo-selectivity of the [Ru(triphos)(tmm)] catalyst enables an unprecedented three component coupling reaction of primary amines, aldehydes and CO2 to produce tertiary N-methylamines in good to excellent yields in only one step generating water as the only by-product.

  Forschungsgebiete der Arbeitsgruppe Heterogene Katalyse Urheberrecht: ITMC RWTH  

Catalytic reductive methylation of imines with CO2 and H2 (A), and one-step synthesis of unsymmetrical tertiary N-methylamines via three components coupling of primary amines, aldehydes and CO2 (B).This method enabled the preparation of the antifungal agent butenafine in one step with no apparent waste, thus increasing the atom efficiency of its synthesis and introducing CO2 as a possible C1 building block for pharmaceutical compounds.

  Forschungsgebiete der Arbeitsgruppe Heterogene Katalyse Urheberrecht: ITMC RWTH  

In our group, we also extended the use of this Ru-Triphos system for the synthesis of chemically valuable trimethylamine TMA via a multicomponent combination of ammonia with carbon dioxide and molecular hydrogen. Using the [Ru(triphos)(tmm)] catalyst together with acid co-catalyst resulted in high ammonia conversion and excellent selectivity for TMA in organic solvents. Aqueous solutions of ammonium chloride were methylated almost quantitatively to the corresponding hydrochloride salt TMA×HCl in a biphasic solvent system using the same Ru-complex without the need for any co-catalyst.

  Forschungsgebiete der Arbeitsgruppe Heterogene Katalyse Urheberrecht: ITMC Aachen

2) "Bio-hybrid" Transformations employing CO2 as C1 building block

  A roundabout demonstrates "Bio-hybrid" transformations with CO2 as C1 building block Urheberrecht: ITMC RWTH

The concept of “bio-hybrid” transformations envisions the integration of biomass and carbon dioxide utilization with molecular hydrogen as an energy vector. Consequently, the combined utilization of carbon dioxide and biobased carbon feedstock offers the option to incorporate renewable energy, paving the way to tailored processes for chemicals and fuels with a largely reduced carbon footprint.


K. Thenert, K. Beydoun, J. Wiesenthal, W. Leitner, J. Klankermayer, Angew. Chem. Int. Ed. 2016, 55, 12266. LINK

S. Deutz, D. Bongartz, B. Heuser, A. Katelhon, L. Schulze Langenhorst, A. Omari, M. Walters, J. Klankermayer, W. Leitner, A. Mitsos, S. Pischinger, A. Bardow, Energy Environ. Sci. 2017. LINK

K.Beydoun, J. Klankermayer, Chem. Eur. J. 2019. LINK

CoverPicture: K.Beydoun, J. Klankermayer, Chem. Eur. J. 2019. LINK

N. Westhues, M. Belleflamme, J. Klankermayer, ChemCatChem, 2019. LINK

N. Westhues, J. Klankermayer, ChemCatChem, 2019. LINK

  Illustration of the Bio-hybrid approach Urheberrecht: ITMC RWTH

Bio-hybrid approach for incorporation of renewable energy in processes with the combined utilization of CO2 and bio-based carbon feedstock


Selective Synthesis of Dialkoxymethanes and cyclic/linear acetals using CO2 and H2:

In our group, we are also investigating a novel catalytic synthesis towards dimethoxymethane (DMM or methylal) starting from methanol, CO2 and H2. This reaction pathway provides the first direct reductive access to DMM, which constitutes the starting member of the oxymethylene-ether series (OME1), currently discussed as potential fuel candidates based on renewable hydrogen. This reaction provides the first synthetic example for the selective conversion of and to the formaldehyde level. The catalytic system was based on the Ru-Triphos unit in combination with Lewis- and/or Brønsted co-catalysts. The multifunctionality of the catalyst system was crucial for the complex reaction sequence, comprising various hydrogenation and esterification/acetalization steps. Moreover the selective synthesis of cyclic and linear acetals from the combined utilization of CO2, H2 and biomass derived diols could also be achieved.

  Pathway for the utilization of CO2/H2 to DMM Urheberrecht: ITMC RWTH

Utilization of CO2/H2 for synthesis of Dimethoxymethane (DMM) starting from methanol and cyclic/linear acetals starting from diols.

  First transferhydrogenation of CO2 to methanol Urheberrecht: ITMC RWTH

Development and application of molecular Ru/E-triphos/Lewis acid catalyst system for the first transfer hydrogenation of CO2 to methanol with linear alcohols.

  Application of tridentate ruthenium phosphine complex for the production of methyl formate Urheberrecht: ITMC RWTH

Application of tailor-made tridentate ruthenium phosphine complexes in the novel homogeneously catalyzed base-free hydrogenation of CO2 to methylformate (MF)


3) CO2 utilization catalyzed by non-precious catalytic systems


B. G. Schieweck, J. Klankermayer, Angew. Chem. Int. Ed. 2017, LINK

B. G. Schieweck, N. F. Westhues, J. Klankermayer, Chem. Sci. 2019, LINK

The development of a tailored catalyst system based on cobalt and nickel salts in combination with selected Triphos ligands and acidic co-catalysts paved the way for the use of non-precious transition-metal catalyst system for the selective synthesis of formate and dialkoxymethane ethers products. This unprecedented productivity based on the molecular cobalt or nickel catalysts is the first example of a non-precious transition metal system for this transformation utilizing CO2 as renewable C1 sources.

  Cobalt Triphos catalyzed CO2 hydrogenation to DMM Urheberrecht: ITMC RWTH

  Nickel catalyzed CO2 hydrogenaton to formates Urheberrecht: ITMC RWTH

Application of the versatile multidentate NP3 ligand in combination with selected nickel(II) salts enabled the effective transformation of CO2 in the presence of molecular hydrogen.