Postsynthetic modification of single Pd sites into uncoordinated polypyridine groups of a MOF as the highly efficient catalyst for Heck and Suzuki reactions

A novel holmium(iii) metal-organic framework (Ho-MOF), namely, [Ho(2-TriPP-COO)(3)] (2) has been hydrothermally obtained using 4-(4-carboxyphenyl)-2,2:6,2-terpyridine (2-TriPP-COOH) and Ho(NO3)(3)5H(2)O, and it is structurally characterized by single-crystal XRD, powder XRD as well as elemental analysis. The postsynthetic modification of Ho-MOF is based on the utilization of a strong coordination effect between Pd2+ ions and free polypyridine groups in the skeleton of Ho-MOF, which play a critical role to access the highly efficient Pd-HoMOF catalyst. Also, Pd-HoMOF exhibits very high activity in Heck and Suzuki-Miyaura cross-coupling reactions. Moreover, the MOF catalyst displays good thermal stability (up to 400 degrees C), and it can be recovered and reused for five reaction cycles. The bridging between the MOF structure and homogeneous molecular Pd catalyst represents a good example in designing highly efficient catalysts for various fine chemical transformations.