Aggregation-Induced Electronic Modulation of Carbon Nitride Nanosheets for Broadband Solar Hydrogen Production.

Photocatalytic hydrogen evolution represents a pivotal technology for sustainable energy conversion, yet its efficiency is fundamentally constrained by the limited light absorption and rapid charge recombination of most semiconductor photocatalysts. Herein, we demonstrate that the controlled aggregation of polymeric carbon nitride (PCN) nanosheet is a powerful strategy to overcome these limitations. We systematically reveal that aggregation fosters spatial electronic interactions, effectively extending the optical absorption of PCN into the red-light region. Furthermore, the accompanying weak noncovalent interactions induce spontaneous symmetry breaking within the aggregates, generating a built-in electric field that suppresses charge recombination. This synergy endows the aggregated PCN nanosheets with enhanced photocatalytic activity, achieving an apparent quantum yield (AQY) of 26.69% at 420 nm. Most notably, we report for the first time that the PCN nanosheet aggregates enable efficient hydrogen evolution under low-energy red light (610 nm), with an AQY of 3.04%, a capability entirely absent in their monomeric form. This study not only provides fundamental insights into aggregation-induced effects but also establishes aggregation engineering as a novel and effective paradigm for designing high-performance, broadband-responsive PCN photosystems.