Catalytic improvement by open metal sites in a new mixed-ligand hetero topic metal-organic framework

A new porous MOF, [Zn2(BDC)1.5(L)(DMF)].1.5DMF, [TMU-41] (L=pyridine 4-carboxylic acid), (BDC= benzene-1,4-dicarboxylate), has been synthesized and fully characterized by single-crystal X-ray crystallography, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and N2 adsorption-desorption isotherms. The values of surface areas obtained are in the range of 740 m2/g after removing the coordinated DMF molecules. The standard procedure is to take the Zn2 group as a single secondary building unit (SBU). Each of these is linked to five others to produce a 5-c net. The net is a high symmetry net with RCSR symbol bnn. Because of presence open metal sites (OMSs) in the Metal-Organic Framework, the framework exhibits specific properties, also the framework can act as a Lewis acid catalyst. In this study, due to the special properties of unsaturated metal sites which act as catalyst, tried to convert the structure with coordinated DMF molecules into open metal sites structure by removal coordinated DMF under a specific condition. Metal-organic framework with the open metal site (TMU-41 (OMS)) was used as a catalyst for the knoevenagel condensation reaction and the catalytic activity of this MOF was investigated in comparison to TMU-41. The result have showed that because of the availability of open metal site in this framework, (TMU-41 (OMS)) with the small amount catalyst (0.008 g), was more efficient than TMU-41 in these reaction.