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Updated: Jun 13, 2025

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
Four-electron reduction of CO2: from formaldehyde and acetal synthesis to complex transformations
Sarah Desmons1, Julien Bonin2,3, Marc Robert2,3,4
1LCC-CNRS, Université de Toulouse, CNRS 205 route de Narbonne 31077 Toulouse Cedex 04 France sebastien.bontemps@lcc-toulouse.fr.
Abstract:
The expansive and dynamic field of the CO2 Reduction Reaction (CO2RR) seeks to harness CO2 as a sustainable carbon source or energy carrier. While significant progress has been made in two, six, and eight-electron reductions of CO2, the four-electron reduction remains understudied. This review fills this gap, comprehensively exploring CO2 reduction into formaldehyde (HCHO) or acetal-type compounds (EOCH2OE, with E = [Si], [B], [Zr], [U], [Y], [Nb], [Ta] or -R) using various CO2RR systems. These encompass (photo)electro-, bio-, and thermal reduction processes with diverse reductants. Formaldehyde, a versatile C1 product, is challenging to synthesize and isolate from the CO2RR. The review also discusses acetal compounds, emphasizing their significance as pathways to formaldehyde with distinct reactivity. Providing an overview of the state of four-electron CO2 reduction, this review highlights achievements, challenges, and the potential of the produced compounds - formaldehyde and acetals - as sustainable sources for valuable product synthesis, including chiral compounds.
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