Ullmann-type coupling reaction using metal-organic framework MOF-199 as an efficient recyclable solid catalyst Original Research Article

A highly porous metal-organic framework (MOF-199) was synthesized, and characterized by several methods including XRD, SEM, TEM, TGA, FT-IR, AAS, and nitrogen physisorption measurements. The MOF-199 was used as an efficient recyclable solid catalyst for the Ullmann-type reaction between aryl iodides and phenols to form diaryl ethers. High conversions were achieved for the transformation at the catalyst concentration of 5 mol%, in the presence of MeONa as a base. Due to the rare availability and the high cost, Cs2CO3 should only be used for the case of deactivated aryl iodides or deactivated phenols. The MOF-199 catalyst could be facilely separated from the reaction mixture by simple filtration, and could be reused several times without a significant degradation in catalytic activity. The Ullmann-type reaction could only proceed in the presence of the solid MOF-199 catalyst, and the contribution from leached active species in the liquid phase, if any, was negligible.