Three-Dimensional Mesoporous Covalent Organic Framework for Photocatalytic Oxidative Dehydrogenation to Quinoline

Developing precious metal-free catalysts for organic reactions under mild conditions is urgent. Herein, we report a three-dimensional covalent organic framework (3D-COF) with high crystallinity and permanent pores, termed 3D-TABPA-COF, for the oxidation of tetrahydroquinoline to quinoline. The 3D-TABPA-COF assembled based on N₄,N₄-bis(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine (TABPA) is the catalytic active center for the conversion of tetrahydroquinoline. The triphenylamine in the structure is an effective photosensitizer, which not only enhances the light absorption capacity but also facilitates the rapid transfer of photogenerated electrons and ensures effective carrier separation. The obtained 3D-TABPA-COF has a high specific surface area (2745.06 m² g^-1) and mesopores of 3.57 nm. This is attributed to the fact that the topology is not easy to interpenetrate. It can oxidize tetrahydroquinoline to obtain quinoline efficiently under visible light irradiation. In addition, we also performed various photochemical characterizations combined with density functional theory calculations to elucidate the reaction mechanism from tetrahydroquinoline to quinoline. This work provides a feasible strategy for constructing 3D-COF to achieve efficient photocatalytic organic reactions.