Photoelectrocatalytic Upgrading of Biomass Derivatives for Efficient C-N Coupling with Formamide.

The formation of the C-N bond plays a pivotal role in the ecofriendly synthesis of fertilizers, pharmaceuticals, and chemical products. Photoelectrocatalytic (PEC) upgrading of biomass derivatives powered by renewable energy offers a green and sustainable catalytic strategy to generate formamide, which has scarcely been explored. Herein, we developed a promising PEC approach for constructing a C-N bond to synthesize formamide through the coupling of the oxidation of biomass derivatives. Taking glucose as a representative, we achieved a high formamide yield of 976.6 mmol m-2 h-1 at 1.2 V versus a reversible hydrogen electrode (vs RHE) and Faraday efficiency (FE), >81% at 0.8-1.2 V vs RHE by integrated photoanode, representing excellent performance in comparison to previous reports for electrosynthesis (FE < 43.2%). Moreover, a large-area (5 × 5 cm2) photoanode was also applied for formamide synthesis, representing an industrial current of 100 mA with FE > 78.1%. To ascertain the mechanism, in situ photoelectrochemical spectroscopy and density functional theory calculations confirmed that the formaldehyde radical (*CHO) intermediate was formed by the direct oxidation of photogenerated holes instead of the hydroxyl radical (*OH) attack to break the C-C bond, and then the C-N bond was established by coupling with *CHO and the nitrogen radical (*NH2) formed by NH3 to form formamide. The substrate could be converted from glucose to biomass-derived aldoses (or polyols), demonstrating its superior reaction suitability. This work deepened the understanding of the C-N coupling mechanism and provided an effective PEC approach for the conversion of biomass derivatives into valuable chemicals.