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

The synthesis of metal-organic frameworks with Bronsted acid moieties is usually tedious and the study of metal-organic frameworks as a heterogeneous Bronsted 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 Bronsted 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.