Superior Catalytic Performance of Hierarchically Micro‐Meso‐Macroporous CuAlPO‐5 for the Oxidation of Aromatic Amines under Mild Conditions

Aromatic nitro compounds are versatile building blocks for organic synthesis because of easy transformation of the nitro group into other diverse functional groups. Herein, hierarchical mesoporous-macroporous CuAlPO-5 was prepared and found to exhibit excellent catalytic activity and stability for the oxidation of aromatic amines to nitroarenes. For the oxidation of bulky aromatic amine molecules (e.g., 1-naphthalenamine), hierarchical CuAlPO-5 exhibited higher selectivity to the product than homogeneous Cu catalysts and higher catalytic activity than traditional microporous CuAlPO-5; the former was attributed to shape selectivity to the product and the latter was attributed to improved diffusion of bulky molecules inside the meso-and macropores. After CuAlPO-5 was used five times in the oxidation of 4-bromoaniline, >98.6% conversion and 98.1% selectivity to the product were obtained. This shows the potential and attractiveness of this method for the preparation of nitroarenes by the selective oxidation of organic amines.