Graphitic Carbon Nitride-Based Photoinitiators for Multi-Wavelength Thiol-Ene Photopolymerization Toward Hydrogel...

Graphitic carbon nitride (g-C₃N₄) based semiconductor photoinitiators have attracted considerable interest for photopolymerization. Although structurally engineered g-C₃N₄ have shown promising photoinitiation performance, how modification-induced changes in material properties affect their photoinitiation ability remains insufficiently understood. Herein, three g-C₃N₄ materials prepared through different structural and chemical modification strategies-CN550 (prepared at 550°C), CN700 (thermally exfoliated), and TACN (tartaric acid-assisted)-are systematically compared as heterogeneous photoinitiators for visible-light thiol-ene photopolymerization. The comparative reveals that thermal exfoliation and tartaric acid-assisted synthesis impart distinct advantages to g-C₃N₄ photoinitiators. CN700 exhibits consistently high photoinitiation ability across 405-530 nm irradiation, benefiting from improved surface accessibility coupled with favorable optical and electronic properties, while TACN shows improved performance under longer-wavelength irradiation due to its enhanced light-harvesting capability. Efficient thiol-ene photopolymerization is achieved in both organic and aqueous systems without additional co-initiators, enabling one-pot fabrication of composite materials. The optimized aqueous formulation is further explored to fabricate conductive hydrogels through NaCl incorporation, while the organic formulation enables direct laser writing for customized patterning. This work demonstrates that the photoinitiation ability of g-C₃N₄ relies on the combined effects of structural accessibility and photophysical properties, providing guidance for the design of semiconductor photoinitiators for visible-light thiol-ene photopolymerization.