Donor-acceptor mixed-ligand MOF with energy transfer-mediated high-efficiency singlet oxygen generation for boosted organic photosynthesis.

Integrating energy donor and acceptor chromophores as ligands within one MOF for advanced artificial photosynthesis is of great interest but appears to be a major challenge. Herein, via a simple one-pot synthetic strategy, an energy acceptor porphyrin ligand 5,15-di(p-benzoato)porphyrin (HDPBP) was successfully integrated into an energy donor 1,4-naphthalenedicarboxylic acid (HNDC)-based MOF (UiO-66-NDC) to construct a mixed-ligand MOF, donated as UiO-66-NDC-HDPBP. Benefiting from the ample overlap between the emission spectrum of HNDC and the absorption spectrum of HDPBP, an efficient energy transfer (EnT) process from the donor HNDC to the acceptor HDPBP within UiO-66-NDC-HDPBP can occur and be captured by time-resolved spectroscopy. Furthermore, the singlet oxygen (O) generation efficiency of UiO-66-NDC-HDPBP mediated by this EnT process as well as the EnT process from the triplet state (T) of the photosensitizer HDPBP ligand to the ground state of molecular oxygen (O) upon light irradiation can be maximized via simply regulating the loading amount of HDPBP, leading to boosted photocatalytic activities toward important aerobic oxidation reactions of amines and sulfides, even under sunlight and ambient air. This work explores an avenue to construct high-efficiency energy donor and acceptor-based light-harvesting systems by utilizing mixed-ligand MOFs as platforms to advanced artificial photosynthesis.