Metal organic framework-supported N-heterocyclic carbene palladium complex: a highly efficient and reusable heterogeneous catalyst for Suzuki-Miyaura C-C coupling reaction

A metal organic framework-supported N-heterocyclic carbene (NHC) was prepared by post-synthetic modification (PSM) of NH₂-MIL-101(Cr). The amine group in the NH₂-MIL-101(Cr) was modified via condensation with 1,3,5-trichlorotriazine (TCT) providing a precursor that then reacted with N-methylimidazole to produce the MIL-101(Cr)-NH₂-bis(NHC). The N-heterocyclic carbene moieties were coordinated with palladium in situ in the porous matrix. The structure of MIL-101(Cr)-NH₂-bis(NHC)-Pd (MIL-NHC-Pd) was confirmed by XRD and FT-IR spectroscopy. Electron microscopy was used to characterize the morphology of the resulting material. XPS and ICP confirmed surface composition while Brauner–Emmett–Teller (BET) analysis was used to define the specific surface area. On testing the catalytic activity, cross-coupling reactions of phenylboronic acid and aryl halides proceeded successfully with MIL-NHC-Pd (0.067 mmol Pd/g) as a heterogeneous catalyst. The catalyst was recovered from the reaction mixture by simple filtration and reused for 15 times without leaching into solution or any loss of activity.