Synthesis of a flower-like Zr-based metal–organic framework and study of its catalytic performance in the Mannich reaction

Abstract

The synthesis of metal–organic frameworks with Brønsted acid moieties is usually tedious and the study of metal–organic frameworks as a heterogeneous Brønsted acid catalyst is limited. In this manuscript, a facile one-step synthesis of UiO-66-(COOH)₂ material with a flower-like morphology has been developed. The as-synthesized flower-like UiO-66-(COOH)₂ can serve as an efficient Brønsted acid in nitro-Mannich and Mannich reactions taking advantage of its morphology assembled from nanoscaled plates. 72–99% yields of Mannich adducts were obtained for a variety of acyl imine substrates in the presence of 0.5 mol% MOF catalyst under extremely mild conditions. Furthermore, the as-synthesized flower-like UiO-66-(COOH)₂ catalyst can be recycled several times without compromising the catalytic activity.