Artificial synthesis of carbohydrates from electrochemically fixed carbon dioxide

Sustainable synthesis of C₅₊ carbohydrates from CO₂ remains challenging due to the complexity of controlled CO₂ reduction and carbon–carbon coupling. Biochemical approaches can convert primary CO₂ reduction products into C₅₊ carbohydrates, but are often constrained by lengthy reaction periods, low production rates and system complexity. Here we present a two-step electrochemical reduction–formose reaction method that uses hydroxymethanesulfonate (HMS) as a more stable surrogate for formaldehyde to facilitate the direct synthesis of C₅₊ carbohydrates from electrochemically fixed CO₂. Using cobalt tetraaminophthalocyanine molecules supported on multiwalled carbon nanotubes as an electrocatalyst, we achieve an HMS Faradaic efficiency of ~12% at a total current density of 150 mA cm⁻². Employing direct CO reduction increases the Faradaic efficiency to ~25% with over 63% carbon efficiency. The produced HMS enables an efficient formose reaction under mild conditions reaching a yield of 20.4% for C₅₊ carbohydrates. The CO₂-derived HMS also demonstrates its versatility as a formaldehyde surrogate in other reactions for synthesizing various valuable chemical products, promising a new approach for feeding advanced chemical synthesis with electrochemically fixed CO₂ via the intercepted formaldehyde intermediate.