Isostructural Perylene Diimide-Based Metal-Organic Frameworks for Efficient Photocatalytic Oxidation of Benzylamines

Incorporating a perylene diimide (PDI)-based ligand into metal-organic frameworks (MOFs) is an effective but scarcely studied strategy for fabricating high-performance photocatalysts. In this work, three isostructural PDI-based MOFs with a formula of [M₃(HTCPDI)₂(H₂O)₄]·2DMF·H₂O (M-TCPDI, where M = Ni(II), Co(II), or Mg(II), H₄TCPDI = N,N'-bis(3,5-dicarboxyphenyl)-1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylic diimide, and DMF = N,N-dimethylformamide) were successfully synthesized under solvothermal conditions. Crystal structure analysis demonstrated that these three MOFs are isostructural three-dimensional (3D) frameworks. In addition to retaining absorption features similar to those of H₄TCPDI in the visible region, these materials exhibit additional pronounced and extended absorption spanning the range of 600-900 nm. To study their capability as photocatalysts, the oxidative coupling of benzylamine to imine was employed as a model reaction and the results revealed that the performance of Ni-TCPDI is slightly better than that of Co-TCPDI, but significantly better than that of Mg-TCPDI, under 50 W white light LED irradiation in air without any other additives. More impressively, Ni-TCPDI could deliver appreciable photocatalytic reactivity under simulated sunlight at a light intensity of 50 mW cm^-2. This study expands the scope of PDI-based MOFs in photocatalysis and offers an effective strategy for light-driven oxidative reactions through rational metal-node modulation.