Rational design of D− π − A− π − D porous organic polymer with polarized π for photocatalytic aerobic oxidation

Charge separation and reactive oxygen species (ROS) generation efficiency are of foremost importance for photocatalytic aerobic oxidation reactions. In this study, four porous organic polymers (POPs), namely JNU-208, -209, -210, and -211, were designed and synthesized from linear bipyrazoles and cyanuric chloride through condensation reactions. The donor−acceptor−donor (D−A−D) type POP (JNU-209) exhibits improved photo-electrochemical properties relative to the donor–π–donor (D−π − D) type POP (JNU-208). Benzene and thiophene were further incorporated respectively as bridging π-units. The two corresponding D− π − A− π − D type POPs (JNU-210 and -211) exhibit additionally enhanced photo-electrochemical properties. The four POPs were examined their potentials as photocatalysts for the aerobic oxidation of benzylamines, and JNU-211 was found to have the highest photocatalytic activity. Theoretical calculations confirm that the introduction of thiophene not only increases the conjugation but also promotes the π-electron polarization, both of which facilitate charge separation and ROS generation.