Linker engineering in UiO-68-type metal-organic frameworks for the photocatalytic thioamide cyclization

Metal-organic frameworks (MOFs) demonstrate strong potential for application in photocatalysis owing to their tunable compositions and structures. However, systematically controlling the photoelectronic properties of MOFs remains a great challenge. Herein, we show that linker engineering is a powerful strategy for systematically tuning the light absorption and charge-separation behavior of UiO-68 type MOF photocatalysts, using benzothiadiazole-based dicarboxylic acids as linkers. Remarkably, the introduction of different benzothiadiazole units onto the linkers led to distinctly different activities of the resulting MOFs (UiO-68, UiO-68-Bs, UiO-68-Ph, and UiO-68-Py). Among these catalysts, the integration of a fully conjugated benzothiadiazole acceptor and pyrene donor into UiO-68-Py allowed it to serve as a highly efficient and recyclable photocatalyst for thioamide cyclization under mild conditions. A mild, green, and sustainable visible-light-driven synthesis of 1,2,4-thiadiazole using a linker engineering method for systematically tuning the light absorption and charge-separation behavior is reported.