Metal free visible light mediated cycloaddition reaction using recyclable graphitic nitride under water

Abstract

The development of environmentally benign photocatalytic methodologies for [2 + 2] cycloadditions is of significant interest, given their utility in accessing cyclobutane motifs found in natural products and pharmaceuticals. Conventional approaches often rely on noble metal photocatalysts, harsh conditions, or organic dyes, limiting sustainability and scalability. Herein, we report a visible-light-driven, metal-free [2 + 2] photocycloaddition of chalcone and styrene derivatives using heterogeneous graphitic carbon nitride (g-CN). Mechanistic and DFT studies reveal an energy transfer (EnT) pathway rather than redox activation. This strategy demonstrates the potential of g-CN to expand beyond redox transformations toward sustainable energy-transfer-driven photocatalysis, offering a green and versatile route to cyclobutane frameworks.