Alkali metal modified carbon nitride enhance photocatalytic performance for highly selective oxidation of benzyl C(sp)-H bonds

Photocatalytic selective oxidation of C(sp3)-H bonds is an attractive strategy for synthesis of high value-added products due to the property of solar-driven and mild reaction conditions. However, improving photocatalytic activity and selectivity is still a grand challenge. Herein, we systematically compared the activity and selectivity for photocatalytic oxidation of 4-phenyltoluene by using the as-prepared photocatalysts. The results demonstrated that structure control and alkali metal modification could improve photocatalytic activity and selectivity by increasing the amount of singlet oxygen (1O2) molecules, which was proved by electron paramagnetic resonance (EPR) spectroscopy and phosphorescence (PH) spectroscopy. Moreover, no apparent decrease of conversion rate and selectivity during the 6 cycle runs indicated excellent stability of the prepared photocatalysts. This work revealed a basic mechanism on the energy transfer process of excitons and developed a feasible strategy for the design of C3N4-based photocatalysts.