Efficient IrIII Photosensitizer Incorporated in the Metal–Organic Framework with the Bis-lophine-bipyridine Motif for C(sp3)-C/N–H Cross-Coupling Reactions

Photocatalytic technology offers a potential solution to energy and environmental issues. The performance of photocatalysts directly affects the efficiency of photocatalysis. Iridium(III)-based catalysts have garnered attention due to their unique electronic structure and high catalytic activity. However, most IrIII catalysts are homogeneous and face issues such as low stability and difficulty in recycling. The research on heterogeneous IrIII catalysts has become a hot topic, aiming to improve their stability and recyclability. In this study, we designed a tetracarboxylate ligand containing bipyridine modified with a bilophthalene unit, constructed a Zr-based metal–organic framework (MOF) with a 2-fold interpenetrating structure, and introduced IrIII(ppy)2+ units through postmodification to form Ir@Zr-MOF. The heterostructure enhanced the utilization of light energy and photocatalytic efficiency. Apart from the electron transfer pathway between the original zirconium clusters and the bis-lophine-bipyridine unit, comparative studies of theoretical models showed that the introduction of the IrIII(ppy)2+ unit reduced the energy level and enhanced the absorption of visible light in the 500–550 nm range, corresponding to the charge transfer between the modified bis-lophine-bipyridine and IrIII(ppy)2+ unit. Ir@Zr-MOF, as a photocatalyst, can facilitate the trifluoromethylation of coumarins and the oxidative dehydrogenative coupling reaction of ethers with aryl hydrazones. The conversion yields of the related reactions can reach up to 95%. The mechanism presumes that the generation of superoxide radicals and the corresponding holes produced by Ir@Zr-MOF are crucial for the photocatalytic reaction. The generation of superoxide radicals can be verified by ESR. The host–guest interactions and hole effects of Ir@Zr-MOF with reaction substrates were also explored through theoretical simulations. This work provides a strategy for the heterogenization of IrIII catalysts, offering insights for the preparation of photosensitizers and the enhancement of light energy utilization.