Highly Enhanced Congo Red Sorption of New Functionalized Porous Eu(III)–Organic Framework by the Insertion of Sulfonate Groups

Due to the development of various industries, the environment is facing serious water pollution problems, especially the pollution of water resources caused by the discharge of organic dyes. Thus, it has become a key research topic for dyeing wastewater treatment technology. In this study, a new three-dimensional (3D) porous metal–organic framework (MOF), {[Eu2(DPNS)2(H2O)4]·4H2O} (DPNS-Eu, H2DPNSNa = sodium 5,8-dicarboxynaphthalene-2-sulfonate) was rationally constructed using a naphthalene carboxylic ligand decorated with a sulfonate group. The structural characteristics of DPNS-Eu were investigated using IR spectra, X-ray single-crystal diffraction, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and ζ-potential. Due to the decoration of sulfonate groups on DPNS-Eu, the adsorption capacity for Congo Red (CR) can reach 1322.9 mg g–1, which is comparable to that of ZIF-8 (1339.8 mg g–1). After five cycles of experiments, the removal efficiency of DPNS-Eu to CR remained 84.39%. Therefore, DPNS-Eu has great potential advantage in the treatment of dyeing wastewater.