Porous Cu-based metal organic framework (Cu-MOF) for highly selective adsorption of organic pollutants

Abstract

In this study, copper based metal organic frame work (Cu-MOF) was synthesized by using different solvents i. e. H2O, Dimethylformamide (DMF) and DMF ​+ ​C2H5OH ​+ ​H2O solutions at various temperatures. Cu-MOF synthesized in different solvents exhibited a large number of properties and advantages including easy synthesis procedure, high porosity, good crystallinity, high surface area, massive pore volume, controllable pore surface properties (zeta potential), rigid and chemical stability. The as-synthesized Cu- MOF was analysed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area, zeta potential, electrostatic attraction and Thermal gravimetric analysis (TGA). A higher BET surface area of 121.1 ​m2 ​g−1 was obtained for Cu-MOF synthesized in DMF ​+ ​C2H5OH ​+ ​H2O compared with H2O (109.3 ​m2 ​g−1) and DMF (115.1 ​m2 ​g−1) solvents. The as-obtained Cu-MOF was used to investigate adsorption kinetic performances of methylene blue (MB) and methyl orange (MO) dye molecules. Compared with other samples, Cu-MOF synthesized in (DMF ​+ ​C2H5OH ​+ ​H2O) has a significantly enhanced adsorption ability for MB but a lower for MO dyes. After 4 ​min, the adsorption co-efficient (k) values were calculated to be 0.506, 0.846 and 1.1915 min−1 for MB and 0.029, 0.024 and 0.005 min−1 for MO dyes for Cu-MOF (H2O), Cu-MOF (DMF) and Cu-MOF (DMF ​+ ​C2H5OH ​+ ​H2O), respectively. It was found that Cu-MOF has a higher adsorption for MB dye but a poor adsorption capacity for MO, which was attributed to the electrostatic attraction/repulsion phenomena. Moreover, compared with Cu-MOF (DMF) and Cu-MOF (H2O), Cu-MOF (DMF ​+ ​C2H5OH ​+ ​H2O) shows an improved stability at 370, 417 and 423 ​°C temperatures. The result obtained through experiment suggested that porous Cu-MOF microstructures synthesized in DMF ​+ ​C2H5OH ​+ ​H2O have potential application for the treatment wastewaters having MB and MO dyes.