Novel Asymmetric Aggregation Strategy to Boost Charge Separation in Carbon Nitride Polymers for High-Performance Hydrogen Photosynthesis

Carbon nitride polymers (CNPs) have drawn broad interdisciplinary attention in the arena of solar energy conversion. However, serious charge carrier recombination caused by intrinsic electron–hole Coulomb interaction remains a fundamental and long-standing challenging scientific problem in the CNP photosystem. In this work, we synthesized small-sized CNP (denoted SS-CNP) and constructed an aggregated SS-CNP photosystem by noncovalent self-assembly. The structures, photophysical properties, and photocatalytic activity of SS-CNP aggregates have been carefully analyzed by various characterization methods. Results confirm that the weak noncovalent interactions endow the SS-CNP aggregates with the ability to undergo a continuous change in their structure and thus result in spontaneous symmetry breaking. The spontaneous symmetry breaking with uneven charge distribution of SS-CNP aggregates enables the establishment of a built-in electric field at the interfaces of aggregates, which accelerates charge separation and prolongs charge lifetime. Impressively, the SS-CNP aggregates realize a record-high apparent quantum yield of 76.4% at 420 nm, which is much higher than those of the existing CNP photosystems. The discovery and insights provided in this work are expected to provide some clues for manipulating charge separation and advancing the in-depth understanding of the role of asymmetric aggregation of photocatalysts during photoredox reactions.