Piezoelectric Metal-Organic Frameworks Mediated Mechanoredox Borylation and Arylation Reactions by Ball Milling.

Herein, metal-organic frameworks UiO-66 and UiO-66-NH 2 were synthesized, and their piezoelectric properties were characterized by piezoresponse force microscopy. Under mechanical agitation, the highly polarized UiO-66 and UiO-66-NH 2 can act as electron donors to reduce aryl diazonium salts, forming the aryl radical species, which further react with bis(pinacolato)diborane or heteroarenes to generate the desired products with broad substrate scope. For all substrates, it was found that the reactions mediated by UiO-66-NH 2 , which exhibited better piezoelectric property, were more efficient than those promoted by UiO-66. Moreover, it was shown that the convenient regeneration of spent catalysts can be reused for promoting mechanoredox reactions without loss of activities by taking advantage of the unmatched repairability of metal-organic frameworks. Mechanistic studies revealed that a radical pathway was involved in these transformations.