Dual enabling photomediated Knoevenagel condensation and alkene perfluoroalkylation reactions by a photoresponsive cadmium–organic framework

Abstract

In this paper, a 3D porous cadmium–organic framework, named [Cd(DDB)_0.5(4,4′-bimp)_0.5(H₂O)]·H₂O (Cd-MOF), was synthesized by hydrothermal synthesis using cadmium acetate (Cd(Ac)₂·2H₂O), 1,4-di(3,5-dicarboxyphenoxy)benzene (H₄DDB) and 4,4-bis (imidazole-1-ylmethyl)biphenyl (4,4′-bimp) as raw materials. The colorless flake-like crystal of Cd-MOF is a 4,4′-bimp-pillared framework based on a 2D network from DDB linked with the dinuclear Cd2 unit. This non-precious metal material exhibits relatively wide light absorption, excellent thermal stability, high cycle recyclability, and a mesoporous specific surface area. Under the excitation of a blue LED (450 nm) light source, the dual photocatalytic activity of the Cd-MOF was realized: the photocatalytic Knoevenagel condensation reaction of aldehydes and malononitrile (yield up to 67–97.6%) and an efficient light-driven olefin-perfluoroalkyl iodide atom transfer radical addition reaction (yield reached 51–94.8%), achieving a “two birds with one stone” effect. Control experiments and theoretical calculations support our proposed radical mechanism. These reactions feature broad substrate applicability, good functional group tolerance and mild conditions. This work broadens the application of MOF-based materials in the field of photocatalysis and provides new ideas for sustainable green organic synthesis in the future.