Ligand-regulated photoinduced electron transfer within metal-organic frameworks for efficient photocatalysis

Abstract

Dye-based metal-organic frameworks (MOFs) have received great attention due to their excellent photochemical stability in photocatalysis. However, the control of photoinduced electron transfer (PET) from dye to substrates rather than to metal nodes is still a challenging task for modern chemistry and organic synthesis, limiting the application of dye-based MOFs in photocatalytic transformations. Herein, we report a new method by introducing a carbonyl group into triphenylamine to form a planar conjugate acridone to compulsively generate a greater degree of conjugation torsion between the dye-based ligands and the metal-carboxylate nodes for controlling the direction of electron flow in the MOF. A new heterogeneous three-dimensional (3D) acridone-based Co-MOF was fabricated by the solvothermal reaction. In comparison with the similar triphenylamine-based Co-MOF, extensive control experiments in combination with density functional theory (DFT) calculations demonstrated that the acridone-based Co-MOF successfully inhibits the intramolecular PET process between the acridone-based ligands and the metal nodes for efficient photocatalytic organic transformations. This new heterogeneous platform exhibits a promising approach to modulating the direction of PET in MOFs by fine modifications of the ligands, thus providing a new avenue to develop multipurpose and flexible catalytic systems.