Research progress in photochemical synthesis of urea through C–N coupling reactions

Urea, as an important organic compound, plays significant role in promoting the development of agriculture, industry and biological sciences. Conventional urea synthesis process requires harsh reaction conditions (high temperature and pressure), making it energy-intensive, emission-intensive, and costly. Photocatalytic C-N coupling is a potentially green and promising alternative strategy for synthesizing valuable urea from CO₂ and inexpensive nitrogen sources (such as N₂, nitrates, ammonia) as feedstocks under ambient conditions using solar energy. However, the specific details of urea photosynthesis have not been systematically reviewed so far. This article reviews the basic principles of photocatalytic urea synthesis, including the fundamentals, key intermediates, product identification and quantification. Meanwhile, it comprehensively summarizes research advances in photocatalytic urea synthesis, with a focus on the application and design principles of photocatalysts in urea production. Finally, the major challenges and prospective research directions in the field of photocatalytic urea synthesis are thoroughly discussed. We hope that this review will provide useful insights to inspire future research and discoveries.