Piezoelectric Metal Organic Frameworks Mediated Mechanoredox Borylation and Arylation Reactions via Ball Milling

Herein, metal organic frameworks UiO-66 and UiO-66-NH2 were synthesized and their piezoelectric properties were characterized by piezoresponse force microscopy. Under mechanical agitation, the highly polarized UiO-66 and UiO-66-NH2 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-NH2 which exhibited better piezoelectric property were more efficient than those promoted by UiO-66. Moreover, we have shown the convenient regeneration of spent catalysts which 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.