Stable Mn(II) metal–organic framework for efficient visible light initiated trifluoromethylation reaction

A 2D Mn-based MOF ([Mn4(PDI)2(DMF)7(H2O)]n (MOF 1)) (H4PDI = 5,5′-(1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl)diisophthalic acid) was synthesized. Visible light excited Mn-PDI unit in MOF 1 oxidizes NaSO2CF3 to generate CF3 radical and enables MOF 1 to exhibit activity for trifluoromethylation of (hetero)arenes under visible light. The unusual stability of MOF 1 in the trifluoromethylation reactions can be attributed to its unique structure, which prevents it from corrosion by acid byproduct. The peeling of MOF 1 to ultrathin nanosheets or partial oxidation of Mn(II) to Mn(III) in MOF 1 led to MOL 1 and NB 1 with significant improved activity for trifluoromethylation reactions, demonstrating the important role of composition and morphology of a catalyst on its performance. The light initiated trifluoromethylation reactions over these Mn-based MOFs was applied to a variety of substrates. This study provides an efficient strategy for synthesis of trifluoromethylated compounds and highlights the potential of MOFs in light initiated organic syntheses.