Metal–organic framework MOF-199 as an efficient heterogeneous catalyst for the aza-Michael reaction

[Display omitted] ► MOF-199 was synthesized and characterized. ► MOF-199 was used as catalyst for the aza-Michael reaction. ► High conversions were achieved using catalytic amounts of the MOF-199. ► The catalyst could be reused. A highly porous metal–organic framework (MOF-199) was synthesized from the reaction of copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid by solvothermal method, and used as a recyclable acid catalyst for the aza-Michael reaction. Physical characterizations of the solid catalyst were achieved by using a variety of different techniques, including X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), dynamic laser light scattering (DLS), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Excellent conversions were achieved under mild conditions in the presence of 5mol% catalyst. The MOF-199 catalyst could be reused several times without a significant degradation in catalytic activity. No contribution from homogeneous catalysis of active species leaching into the liquid phase was detected.