Defect-Regulated Two-Dimensional Superlattice of Holey g-C 3 N 4 - TiO 2 Nanohybrids: Contrasting Influence of Vacancy Content on Hybridization Impact and Photocatalyst Performance.

Defect engineering provides an effective way to explore efficient nanostructured catalysts. Herein, we synthesize defect-regulated two-dimensional superlattices comprising interstratified holey g-C 3 N 4 and TiO 2 monolayers with tailorable interfacial coupling. Using this interfacial-coupling-controlled hybrid system, a strong interdependence among vacancy content, performance, and interfacial coupling was elucidated, offering key insights for the design of high-performance catalysts. The defect-optimized g-C 3 N 4 -TiO 2 superlattice exhibited higher photocatalytic activity toward visible-light-induced N 2 fixation (∼1.06 mmol g -1 h -1 ) than defect-unoptimized and disorderly assembled g-C 3 N 4 -TiO 2 homologues. The high photocatalytic performance of g-C 3 N 4 -TiO 2 was attributed to the hybridization-induced defect creation, facilitated hydrogenation of adsorbed nitrogen, and improvement in N 2 adsorption and charge transport. A comparison of the defect-dependent photocatalytic activity of g-C 3 N 4 , g-C 3 N 4 nanosheets, and g-C 3 N 4 -TiO 2 revealed the presence of optimal defect content for improving photocatalytic performance and the continuous increase of hybridization impact with the defect content. Sophisticated mutual influence among defect, electronic coupling, and photocatalytic ability underscores the importance of defect fine control in exploring high-performance hybrid photocatalysts. Along with the DFT calculation, the excellent photocatalyst performance of defect-optimized g-C 3 N 4 -TiO 2 can be ascribed to the promotion of the uphill *N hydrogenation step as well as to enhancement of N 2 adsorption, charge transfer kinetics, and mass transports.