Intermediate-induced repolymerization for constructing self-assembly architecture: Red crystalline carbon nitride nanosheets for notable hydrogen evolution

Few-layered polymeric carbon nitride (PCN) nanosheets with large specific surface area and effective charge/electron transport pathway have emerged as promising photocatalysts. However, PCN nanosheets normally exhibit enlarged bandgap, structural defects, and easy agglomeration. Herein, we report an intermediate-induced strategy for synthesizing red PCN nanosheets with a crystalline free self-assembly (CFSA) architecture, exhibiting a three-dimensional (3D) structure, minimum structural defects, small curved nanosheet subunits, and abundant reactive sites. The careful tuning of the condensation degree and repolymerization ability of intermediates affords CFSA PCN with an optimal 3D structure and optical properties, enabling the synergistic optimization of light absorption, charge mobility, and surface reactions during photocatalysis. The catalyst shows a superior H-2 evolution rate of 14665 mu mol g(-1) h(-1) (Pt 1.1 wt%), outperforming those of pristine bulk and nanosheet-structured PCN. This work provides a facile intermediate-induced strategy for guiding the design and synthesis of novel PCN-based photocatalysts.