Pyrene as a Triplet Acceptor Enhancing Triplet Energy Transfer of g-C3N4 in Heterogeneous Photooxidation

Abstract

Triplet photosensitizers have great potential in selective photooxidation by generating 1O2 through triplet energy transfer. However, the heterogeneous bulk photosensitizers easily trap triplet excitons and inhibit photocatalysis efficiency. Previous work focused on controlling ultra-small size to reduce the transfer distance, but we propose a new strategy using triplet acceptor molecules (e.g., pyrenecarboxylic acid, PCA) with proper energy levels to modify the surface of heterogeneous photosensitizers (e.g., g-C3N4), facilitate the transfer of triplet excitons from the interior to the surface of the catalyst, and enhance catalytic reactions on its surface. In the photooxidation reaction of uric acid (UA), the conversion of UA catalyzed by pg-C3N4/PCA can reach 91.3% at 60 min, higher than that without modification (24.0%). DFT calculations and spectroscopic characterization show that the triplet acceptor in pg-C3N4/PCA could reduce the ΔEST value and grab triplet excitons in g-C3N4, thereby enhancing the 1O2 generation. This work provides another approach for high-efficiency utilization of heterogeneous triplet photosensitizers in wide applications.