An open metal site metal–organic framework Cu(BDC) as a promising heterogeneous catalyst for the modified Friedländer reaction Original Research Article

A crystalline porous metal–organic framework Cu(BDC) was synthesized, and characterized by several techniques, including 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), hydrogen temperature-programmed reduction (H2-TPR), and nitrogen physisorption measurements. The Cu(BDC) exhibited high catalytic activity for the modified Friedländer transformation using 2-aminobenzyl alcohol as the starting material, thus offering advantages over the conventional Friedländer reaction in terms of avoiding the problems associated with the storage of the highly unstable 2-aminobenzaldehyde. Moreover, the Cu(BDC) could offer significantly higher catalytic activity than that of other Cu-MOFs such as Cu3(BTC)2, Cu(BPDC), and Cu2(BDC)2(DABCO). The catalyst could be recovered and reused several times without a significant degradation in catalytic activity. The modified Friedländer reaction could only occur in the presence of the solid Cu(BDC) with no contribution from leached active species.