Modulating active sites and reaction pathways: recent progress in photocatalyst design for urea synthesis

As a cutting-edge direction at the intersection of artificial photosynthesis and green chemistry, photocatalytic synthesis of urea is committed to using solar energy to directly couple CO₂ with N₂ or NO₃^- under mild conditions to convert them into high-value urea (CO(NH₂)₂), providing an innovative path for achieving carbon neutrality and sustainable nitrogen cycling. The core challenges of this reaction lie in the high chemical inertness of CO₂ and N₂ molecules, the complex multi-electron/proton transfer processes, and the severe constraints on selectivity caused by thermodynamically favorable side reactions such as the hydrogen evolution reaction. This review systematically describes the basic principles, key intermediates, product identification, and quantification of photocatalytic urea synthesis. Meanwhile, the research progress in materials design for photocatalytic urea synthesis is comprehensively summarized, such as defect engineering, structural engineering, metal doping, and heterojunction construction, with a focus on the structure-activity relationship. We hope that this review can provide useful insights to drive the further development of photocatalytic synthesis of urea.