Polycyclic Heteroaromatics with Planar-Curved Hybrid Skeletons for High-Performance Photocatalytic Hydrogen Peroxide...

Creating curvature in the scaffolds of polycyclic aromatic hydrocarbons (PAHs) enables breaking their molecular planarity or even symmetry, leading to some exceptional optoelectronic activities and assembling behaviors, but rarely explored for promoting photoredox catalysis. Herein, we report the synthesis of two PAHs through the fusion of N-arylcarbazole on one side of a dibenzophenalene precursor edged with a pristine zigzag nitrogen (N)-boron (B)-nitrogen (N) unit. Their unique planar-negatively curved molecular skeletons were revealed by X-ray single crystal structure analysis. Fusing another benzene ring at the terminal positions of such kinds of PAH molecules resulted in a more contorted structure, which led to the successive reversible electrochemical behaviors, stronger hydrophilicity, and better photogenerated charge generation and separation as evidenced by experimental and theoretical data. Upon visible-light activation, the as-prepared PAHs showed a curvature-strengthened photocatalytic activity of hydrogen peroxide (H₂O₂) production (yield: up to 6696 µmol h^-1 g^-1) with good recyclability and reusability. Finally, the femtosecond transient absorption spectra (fs-TAS) indicate that the more curved structure Nap-NBN-PAH has more photogenerated charges and a longer excited state lifetime, which is consistent with better photocatalytic performance.