Ultrathin CoO nanosheets enable direct CO2 hydrogenation to acetic acid.

Direct hydrogenation of carbon dioxide (CO2 ) to acetic acid, a key commodity chemical, offers a sustainable route to valorize greenhouse gases but is plagued by CO2 inertness, thermodynamic barriers, and poor selectivity for C-C coupling over competing overhydrogenation. This paper describes the design and synthesis of ultrathin cobalt(II) oxide nanosheets (<4 nm thick) that achieve direct one-step CO2 hydrogenation to acetic acid with over 90% selectivity, minimal C1 by-products and the highest reported yield under mild conditions, surpassing traditional multistep routes (such as CO2 to CO/methanol followed by carbonylation) in cost, efficiency, and atom economy. These two-dimensional structures feature extended terraces that undergo in situ reconstruction in CO2/H2 mixtures to a cobalt(II) carbonate hydroxide-like phase, stabilizing Co2+ and generating abundant hydroxyl groups to optimize CO2 activation and selective C-C coupling while suppressing over-reduction. In situ characterizations, including electron energy-loss near-edge structure, spatially resolved infrared spectroscopy, and kinetic/isotopic analyses, reveal the reconstructed phase's role in modulating electron density for superior yields and confirm a formate-coupling mechanism unattainable with conventional catalysts. This study introduces a paradigm for CO2 upgrading: harnessing dynamic surface reconstructions and nanoscale morphology to access elusive multicarbon pathways, with implications for sustainable chemical synthesis.