Regioselective oxidative bromination of arenes by a metal–organic framework-confined mono-bipyridyl iron(iii) catalyst†

Abstract

Oxidative bromination of arenes is an effective and environmentally friendly method for synthesizing bromoarenes. We have developed a highly robust zirconium metal–organic framework (MOF)-supported mono-bipyridyl iron(III) chloride catalyst (bpy-UiO-FeCl₃) for oxidative bromination of arenes using H₂O₂ as the oxidant and KBr as the bromine source. The bpy-UiO-FeCl₃ catalyst exhibits high conversion rates for various substituted arenes, yielding significant amounts of bromoarenes with excellent regioselectivity and recyclability under mild reaction conditions. The MOF catalyst outperforms its homogeneous counterparts in terms of both activity and regioselectivity due to the stabilization of the mononuclear bipyridyl-iron(III) species within the active sites within the MOF pores. Furthermore, the confinement of these active sites within the robust, well-defined, and uniform porous framework enhances the regioselectivity of bromination through shape-selective catalysis. The mechanism of bpy-UiO-FeCl₃-catalyzed oxidative bromination of arenes was thoroughly investigated by a combination of control experiments, spectroscopic analyses, and computational studies. These findings underscore the importance of MOFs in the development of heterogeneous catalysts based on Earth-abundant metals for the sustainable synthesis of haloarenes.