g-C₃ N₄ Inverse Opals with Isotype Heterostructure for Enhanced Visible-Light-Driven Photocatalysis

The photocatalytic activity of g-C₃ N₄ is limited by the low surface area and the fast recombination of photogenerated charges. In this work, a g-C₃ N₄ quantum dot (CNQDs) modified g-C₃ N₄ inverse opal (CN IO) metal-free composite (CNQDs/CN IO) was successfully synthesized by a simple calcination method. CNQDs/CN IO exhibited outstanding photocatalytic activity in the removal of organic pollutants represented by phenol, which can be ascribed to (i) the inverse opal structure that enhances the light harvesting, facilitates mass transfer, and provides adequate surface area for photocatalytic reactions; (ii) the incorporation of CNQDs in the framework of g-C₃ N₄ promotes photogenerated charge separation and transfer across the interfaces between CN IO and CNQDs, leading to excellent photoelectrochemical properties. The strategy of self-modification of g-C₃ N₄ with special structures provides a rational design idea to fabricate highly efficient metal-free photocatalysts.