Metal-Organic Layers as Multifunctional Two-Dimensional Nanomaterials for Enhanced Photoredox Catalysis

Metal-organic layers (MOLs) have recently emerged as a novel class of molecular two-dimensional (2D) materials with significant potential for catalytic applications. Herein we report the design of a new multifunctional MOL, Hf₁₂-Ir-Ni, by laterally linking Hf₁₂ secondary building units (SBUs) with photosensitizing Ir(DBB)[dF(CF₃)ppy]₂⁺ [DBB-Ir-F, DBB = 4,4'-di(4-benzoato)-2,2'-bipyridine; dF(CF₃)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine] bridging ligands and vertically terminating the SBUs with catalytic Ni(MBA)Cl₂ [MBA = 2-(4'-methyl-[2,2'-bipyridin]-4-yl)acetate] capping agents. Hf₁₂-Ir-Ni was synthesized in a bottom-up approach and characterized by TEM, AFM, PXRD, TGA, NMR, ICP-MS, UV-vis, and luminescence spectroscopy. The proximity between photosensitizing Ir centers and catalytic Ni centers (∼0.85 nm) in Hf₁₂-Ir-Ni facilitates single electron transfer, leading to a 15-fold increase in photoredox reactivity. Hf₁₂-Ir-Ni was highly effective in catalytic C-S, C-O, and C-C cross-coupling reactions with broad substrate scopes and turnover numbers of ∼4500, ∼1900, and ∼450, respectively.