Synthesis and Structure of Three New Alkaline Earth Metal–Organic Frameworks with High Thermal Stability as Catalysts for Knoevenagel Condensation

Three new alkaline earth metal–organic frameworks (MOFs), [Mg2(BDC-OH)2­(DMF)3] (Mg-HBDC), [Ca­(BDC-OH)­(DMF)2] (Ca-HBDC), and [Sr­(BDC-OH)­(DMF)] (Sr-HBDC) (BDC-OH = 2-hydroxyterephthalate(2−) anion and DMF = N,N-dimethylformamide), were synthesized by the assembly of BDC-OH and nitrate salts of the metal ions under solvothermal conditions. Single-crystal structure analysis revealed that Ca-HBDC and Sr-HBDC are isostructural to their corresponding MOFs containing 2,5-dihydroxyterephthalalate(2−) anion (H2dhtp) and terephthalate(2−) anion (BDC), respectively. The MOFs were also characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. The obtained MOFs were applied as heterogeneous basic catalysts for the Knoevenagel condensation reaction at room temperature. The catalysts showed good catalytic activity and structural stability in the condensation reaction and could be reused without observable loss of activity