Removal of dyes from aqueous solution using zinc terephthalic acid metal-organic frameworks (Zn-TPA-MOF) based adsorbent

Zinc (II)-terephthalic acid metal-organic framework (Zn-TPA-MOF) was synthesized by a solvothermal method ‎and characterized by Scanning Electron Microscope/Energy Dispersive X-Ray (SEM/EDX), Fourier Transformer ‎Infrared (FTIR), Raman, and X-ray diffraction (XRD). Raman microscopy and XRD expose that terephthalic ‎acid (TPA) acts as a bidentate ligand towards zinc(II) through the two carboxylate groups. FTIR and Raman ‎microscopy emphasize the formation of coordination bonds between the electron-acceptor Zn(II) atoms and the ‎electron-donor oxygen atoms. SEM shows that the (Zn-TPA-MOF) has a bar-like macro-structure with small ‎dimensions, e.g., 200 nm. (Zn-TPA-MOF) the structure is proposed to be a cationic metal-organic framework and ‎extremely water-stable. Due to these features, (Zn-TPA-MOF) was studied for the Removal of cationic and ‎anionic dyes, using synthetic cationic dye as Methylene Blue (MB+) and an anionic dye as Congo Red (C.R.-) in ‎an aqueous solution. Zn-TPA-MOF has a strong adsorption potential for both C.R. and M.B. due to the ‎maximum adsorption capacity of C.R. (769.23 mg/g) and MB (147.06 mg/g) onto Zn-TPA-MOF. ‎