Ketone-functionalized conjugated organic polymers boost red-light-driven molecular oxygen-mediated oxygenation

Photocatalytic molecular oxygen activation has emerged as a valuable tool for organic synthesis, environmental remediation and energy conversion. Most reported instances have relied on high-energy light sources. Herein, 9-fluorenone-functionalized porous organic polymers (POPs) were reported to enable red-light-excited photocatalysis for the organic oxygenation reaction. Notably, this modification extends the conjugated backbone, allowing the capture of lower-energy light. Incorporating ketone groups into POPs also facilitates charge separation and enhances carrier concentration, thereby promoting catalytic efficiency. The new POP photomaterials exhibit high activity for the direct α-oxygenation of N-substituted tetrahydroisoquinolines (THIQs) using O₂ as a green oxidant under 640 nm light irradiation, achieving high yield in short reaction times. Detailed mechanistic investigations clearly showed the role of oxygen and the photocatalyst. This work provides valuable insights into the potential of ketone-modified POPs for superior photocatalytic activation of molecular oxygen under low-energy light conditions.