Constructing an Isopolymolybdate-Based Bifunctional Photocatalyst for Promoting Nitroaromatic Reduction and C–H Oxidation

Amide compounds are widely present in drug molecules and natural products, which can be synthesized by acid-amine condensation. It is urgent to design new photocatalysts for achieving both nitroaromatic reduction and C-H oxidation to obtain raw materials, carboxylic acids, and aromatic amines. Herein, a novel isopolymolybdate-incorporated photoactive metal-organic framework, <b>NiMo</b>₁₂-TPT, was constructed by combining the oxidation catalyst [Mo₁₂O₄₀]^8-, Ni(II) cation, and photosensitive ligand 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT). In the structure, the superior electron storage capacity of [Mo₁₂O₄₀]^8-, with its multiple metal centers containing d-electrons, is conducive to providing electrons for the reduction of nitrobenzenes. The donor-acceptor structure of the TPT facilitates the separation of intramolecular charges. Furthermore, the π···π interactions between the TPT molecules promote the transfer of electrons and enhance the performance of photocatalysis. Under illumination, <b>NiMo₁₂-TPT</b> can activate the C-H bonds to generate carboxylic acids with excellent selectivity and simultaneously realize the multistep proton-coupled electron transfer (PCET) process for nitroaromatic reduction. Moreover, EPR tests and the quenching experiments indicated that •O₂^- is the main reactive oxygen species (ROS) in the photocatalytic redox reaction process.