Light-Driven Olefin Epoxidation via Poly(Triazine Imide): A Route Towards Sustainable Epoxide Production

The selective and sustainable synthesis of epoxides remains a critical challenge in chemical industry, as conventional oxidation routes often rely on transition metals, hazardous oxidants, and energy-intensive conditions, resulting in poor atom economy and limited sustainability. Herein, we report a transition-metal-free photocatalyst system capable of promoting olefin epoxidation under mild conditions. Poly(triazine imide) (PTI), a highly crystalline carbon nitride, achieves near-quantitative styrene conversion with good selectivity toward styrene oxide under visible-light irradiation, using molecular oxygen (O 2 ) as the sole oxidant and without the need for stoichiometric oxidants, chemical additives and harsh conditions typical of traditional protocols. A comprehensive structural and optoelectronical characterization was performed to correlate catalytic performance with the intrinsic properties of the material. Furthermore, mechanistic investigations were conducted to identify the key reactive species involved in the reaction. In situ EPR spin-trapping experiments reveal the cooperative involvement of photogenerated charge carriers and radical superoxide (O₂•⁻), driving the selective epoxidation process and singlet oxygen as the responsible for the byproducts. Overall, these findings highlight PTI as an efficient metal-free photocatalyst for O 2 -driven olefin epoxidation and demonstrate the potential of crystalline poly(triazine imide) materials as promising platforms for sustainable oxidation processes. • Crystalline PTI enables metal-free photocatalytic epoxidation using O2 as the sole oxidant under mild conditions; • The system operates without additives, offering advantages in sustainability, atom economy, and operational safety; • A radical-mediated mechanism involving O₂•⁻ (epoxide formation) and ¹O₂ (overoxidation) controls activity and selectivity; • The paper expands the application of PTI materials beyond water splitting toward selective organic oxidation.