Immobilization of Cu Complex into Zr-Based MOF with Bipyridine Units for Heterogeneous Selective Oxidation

Abstract

A catalytically competent Cu species has been immobilized within the framework of a Zr-based metal–organic framework with bipyridine units, Zr-MOF-bpy, by a simple postsynthetic modification method from CuBr2 (Zr-MOF-bpy-CuBr2) and used for the selective oxidation of cyclooctene to cyclooctene oxide. Zr-MOF-bpy was synthesized by a simple solvothermal method and was shown to have a UiO-type structure. Diffuse reflectance UV–vis and XAFS measurements have revealed that the immobilized Cu species has a square-planar geometry of two N atoms and two Br atoms. Zr-MOF-bpy-CuBr2 catalyzed the selective oxidation of cyclooctene to cyclooctene oxide with high activity and selectivity in the presence of tert-butyl hydroperoxide as an oxidant. In addition, the catalytic ability of Zr-MOF-bpy-CuBr2 was demonstrated to be superior to that of the corresponding homogeneous catalyst ((bpy)CuBr2). It was also confirmed that Zr-MOF-bpy-CuBr2 can be reused as a heterogeneous catalyst without significant loss of its activity and selectivity.