Nickel-catalyzed oxidative coupling of alkynes and arylboronic acids using the metal–organic framework Ni2(BDC)2(DABCO) as an efficient heterogeneous catalyst†
Abstract
A crystalline porous metal–organic framework Ni2(BDC)2(DABCO) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Ni2(BDC)2(DABCO) could be used as an efficient and recyclable heterogeneous catalyst for the cross-coupling reaction between phenylboronic acids and phenylacetylenes in the presence of molecular oxygen in air as the stoichiometric oxidant. High conversions of the cross-coupling products were achieved with no homo-coupling products being detected by GC. Ni2(BDC)2(DABCO) exhibited significantly higher catalytic activity in the coupling reaction than that of other Ni-MOFs such as Ni3(BTC)2 and Ni(HBTC)(BPY). Zn2(BDC)2(DABCO) and Co2(BDC)2(DABCO) were found to be completely inactive for the transformation, while the reaction using Cu2(BDC)2(DABCO) as the catalyst led to the formation of a 10% homo-coupling product. To the best of our knowledge, a nickel-based catalyst was not previously used for the oxidative coupling reactions between phenylacetylenes and phenylboronic acids.