Electron Donor Regulation in A-D-A Type Metal-Organic Frameworks for Enhancing Visible-Light Driven Photocatalysis.

Charge separation efficiency is the determinant factor for reactive oxygen species (ROS) involved in photocatalytic aerobic oxidation reaction. Metal-organic frameworks (MOFs) provided a formidable platform for designing a donor-acceptor (D-A) system with tunable photoexcited carrier dynamics. Herein, we reported a series of UiO-68 type MOFs (termed as UiO-68-A-D1-A, UiO-68-A-D2-A, and UiO-68-A-D3-A) based on linearly bridged bis-benzothiadiazole as A-D-A linkers. Experimental and density functional theory calculations revealed that regulating the donor units from benzene to naphthalene and anthracene with gradually improved electron-donating capacity significantly enhanced the photogenerated charge separation and transfer efficiency and hence facilitated the ROS generation. As expected, anthracene-containing UiO-68-A-D3-A displayed the highest activity for the visible-light driven aerobic oxidation of benzylamines coupling. This work demonstrated that linker engineering of D-A molecular junctions in MOFs by fine-tuning the electronic nature of donor and acceptor units and their connection mode is a promising strategy to develop novel photocatalysts for efficient organic transformation.