Honeycomb‐Like g‐C3n4 for Efficient Cross‐Dehydrogenative Coupling Reaction of Tetrahydroisoquinolines

Cost‐effective and efficient photocatalysis is highly desirable in chemical synthesis. Here a honeycomb‐like porous carbon nitride (P‐C 3 N 4 ) with defects was prepared by a simple one‐step calcination of an aqueous urea solution. By introducing the hierarchical porous structure and defects, the P‐C 3 N 4 was able to make more efficient use of visible light and enhance mass transfer. This catalyst exhibits 44% longer carrier lifetime than bulk C 3 N 4 and can be easily scaled up and demonstrates excellent catalytic reactivity in various types of cross‐dehydrogenative coupling (CDC) reactions under visible light irradiation. A very high reaction rates of 6467 and 10,625 μmolg −1 h −1 were achieved by P‐C 3 N 4 in model reaction of aza‐Henry type and Mannich type of CDC reaction, which are 26.8 and 2.8 times higher than previous reports, respectively. Moreover, P‐C 3 N 4 can maintain 95% yield of target product in aza‐Henry CDC reaction after 21 cycles of repeated experiments . Our low‐cost, easy‐to‐process, and highly efficient C 3 N 4 photocatalyst is expected to bring new insights in chemical synthesis.