Single bond regulated 1O2 and ‧O2− selective generation of heptazine-based conjugated polymers for high-selectivity photocatalysis

In conjugated polymers (CPs) photocatalytic system, the generation of reactive oxygen species (ROS) is regulated by cross-scale factors involving active site, excitonic behavior and O 2 activation process on the surface. However, research on exploring the domino effect of “structure → excitonic behavior → O 2 activation → photocatalytic reaction” through structural modification at the atomic scale remains at its early stages. Herein, two heptazine-based CPs, CP-DPA and CP-CZ, were successfully prepared by polymerization of precursors formed by reacting diphenylamine (DPA) and carbazole (CZ) with cyameluric chloride, respectively. The minute difference in single bond between DPA and CZ endows the polymers with distinct physicochemical properties. Owing to the rotation between benzene rings, CP-DPA exhibits relatively lower conjugation, resulting in increased exciton binding energy ( E b ) and inhibited exciton dissociation. Meanwhile, its more triplet state excitons facilitate energy transfer to generate singlet oxygen. Therefore, CP-DPA shows excellent activity for phenylboronic acid oxidation. Conversely, CP-CZ possesses relatively higher conjugation, minimal E b and intensified exciton dissociation, which promotes charge transfer to produce superoxide radical. Consequently, CP-CZ displays optimal activity for phenylacetylene oxidation and [3+2] cycloaddition. This work provides new insights into regulating ROS generation by modulating the composition and structure of photocatalysts at the atomic scale. Two heptazine-based conjugated polymers (CPs) with distinct physicochemical properties, excitonic behavior and photocatalytic performance due to minute single bond differences between diphenylamine (DPA) and carbazole (CZ) have been successfully prepared. Owing to the rotation between benzene rings, CP-DPA exhibits relatively higher triplet state exciton concentration, which makes it tend to perform energy transfer to generate 1 O 2 . Conversely, CP-CZ possesses higher conjugation and stronger exciton dissociation, and is more inclined to undergo charge transfer to produce •O 2 - . Thus, CP-DPA and CP-CZ display high-selectivity in 1 O 2 and •O 2 - -driven reactions, respectively, which provides new insights into the rational design of efficient and highly selective polymer photocatalysts. • Two heptazine-based conjugated polymers with distinct photocatalytic activity were prepared. • Single-bond regulated CP-DPA and CP-CZ exhibit quite different exciton behavior. • ISC and exciton dissociation cause the production of 1 O 2 and •O 2 - , respectively. • Structure-property-mechanism relationships between materials are revealed in depth. • This work provides new insights into the rational design of polymer photocatalysts.