Ethanol photosynthesis from CO₂ and H₂O via a formate intermediate pathway

Photocatalytic CO₂-to-ethanol conversion offers an interesting route for intermittent solar energy utilization. However, the performance is impeded by slow mass-transfer and high dimerization barrier (>1.0 eV) of *CO intermediates, coupled with a kinetic mismatch between the short-lived carriers and the 12 e⁻ reaction. Herein, we develop a Z-scheme Cu^δ+O/floral-like BN photocatalyst that achieves CO₂-to-ethanol conversion with near 100% selectivity. The photocatalyst utilizes the three-dimensional structure and alkaline surface of BN to concentrate CO₂ and directs transfer of long-lived carriers to unsaturated Cu⁺ sites, stabilizing them for flexible electron donation to the π* orbital of CO₂. Enhanced ethanol photosynthesis activity/selectivity stems from a new pathway: CO₂ is first reduced to HCOOH at Cu^δ+O sites, lowering the C-C coupling barrier to 0.44 eV. Liquid formate is then concentrated and protonated to C₂ precursor, minimizing side reactions for high selectivity. Here, we show the feasibility of selective ethanol photosynthesis and uncovers a new formate intermediate pathway.