Unveiling the mechanism on photocatalytic singlet oxygen generation over rationally designed carbonylated carbon nitride

Abstract

Singlet oxygen (¹O₂) with electrical neutrality and long lifetime exhibits great potential in environmental remediation. However, the production of ¹O₂ from O₂ is greatly limited by spin-forbidden transitions. Herein, we elaborate on carbonylated carbon nitride (Ox-CN), which exhibits excellent ability for ¹O₂ generation. Based on the characterization results and theoretical calculations, the introduced carbonyl functional group improved the spin–orbit coupling (SOC) inside polymer carbon nitride (PCN) to reduce the energy gap between singlet states (S) and triplet states (T), thus promoting the intersystem-crossing (ISC) process. As a result, the excitons inside PCN achieved a fast transition from S to T, and the generated T excitons underwent energy transfer with O₂ to produce ¹O₂. Therefore, Ox-CN presents outstanding photocatalytic performance for sulfamethoxazole degradation under different water environmental conditions, thus holding great promise for water treatment. This work provides a theoretical basis for designing a photocatalytic system to generate ¹O₂ for water environmental remediation.