Dual-Function Donor Engineering of a Metal-Organic Framework for Efficient Photocatalytic Oxidative Synthesis

Donor and/or acceptor engineering that allows the delicate optimization of the charge or energy transfer process within heterogeneous photocatalysts for the efficient generation of reactive oxygen species (ROS) of the superoxide radical (O2•-) or singlet oxygen (1O2) dictates the efficiency of aerobic oxidative synthesis. However, the development of donor and/or acceptor engineering approaches that can simultaneously optimize the charge and energy transfer processes for abundant generation of O2•- and 1O2 is a major challenge. Herein, a series of porphyrin (electron donor)- and naphthalene diimide (NDI, electron acceptor)-based isostructural mixed-ligand donor-acceptor MOFs were designed and synthesized. Experiments and theoretical calculations revealed that by delicately tuning the electron-pushing capacity of the organic conjugated groups on the donor porphyrin units, the charge transfer kinetics from the donors to the acceptors as well as the energy transfer gifted by the donor porphyrins related to their singlet-triplet energy gaps could be simultaneously optimized. As a result, Zr-NDI-H2DPBP(Pyr), wherein the porphyrin donor ligand with pyrene (Pyr) groups possesses the strongest electron-pushing capacity, exhibited the highest O2•- and 1O2 generation activities, which can be utilized for efficient aerobic oxidation reactions, including dipolar [3 + 2] cycloaddition and the synthesis of quinoxaline derivatives. This work exemplifies a dual-function donor engineering approach for developing heterogeneous catalysts toward advanced artificial photosynthesis.