Recent advances in the heterogeneous photochemical synthesis of C-N bonds
Over the decades, photochemistry has received great attention and become a powerful tool in organic synthesis. The heterogeneous photocatalysts present complementary advantages in production separation, catalyst recycling, and stability compared to the traditional homogeneous photocatalyst. In this review, we choose the C-N bond formation as a typical coupling reaction and summarize the development of the heterogeneous catalytic system and its advantage. The titanium dioxide, semiconductor quantum dots, covalent organic frameworks, and carbon nitrides would be discussed in detail as important heterogeneous photocatalysts. The combination and electron transfer pathway between heterogeneous catalysts and transition-metal catalysts are the focus of this review. These advances do not only limit the C-N coupling but also extend to the other coupling reactions.