Metal Pyrazolyl-diphosphonate Pillared Materials as Heterogeneous Catalysts in the Mukaiyama-type Aerobic Olefin Epoxidation.

The structural variability and chemical stability of metal phosphonates under harsh conditions are attractive attributes that have drawn considerable attention in recent years. As the needs for more sustainable solutions rise, the demand for novel and tolerant materials also increases. Thus, herein we report, for the first time, the synthesis of a novel diphosphonic organic linker named pyrazole diphenyl phosphonate (PZDP), envisioning the fabrication of durable metal phosphonates. In view of this, a series of M-PZDP materials (M = Ca, Sr, Ba, Zn and Co) were synthesized employing either solvothermal or hydrothermal methods. The crystal structures of the Ca, Sr, Zn, and Co derivatives were determined revealing a 2D-pillared architecture. Zn-PZDP is an anionic framework with dimethylammonium cations. The Co-PZDP compound was tested as a heterogeneous catalyst in olefin epoxidation employing molecular oxygen.