Investigation of the aqueous adsorption capacity of a 6-connected Zr-MOF for anionic and cationic dyes in comparison with other traditional porous materials

Abstract

A 6-connected Zr-MOF (MOF-808) was successfully synthesized via the solvothermal method with the assistance of formic acid (HCOOH). The resulting MOF showed high crystallinity and thermal stability, which was verified by powder X-ray diffraction (PXRD) measurement, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). As can be expected, the obtained material possessed high porosity with an extremely high specific BET surface area (SABet) of 2372 m2/g. The adsorption capacity of MOF-808 for anionic dyes (i.e. sunset yellow, quinoline yellow, and methyl orange) and cationic ones (i.e. methylene blue and malachite green) in aqueous solutions was respectively investigated. For comparison purpose, the adsorption experiments were also carried out using other traditional porous materials, including commercial microporous activated carbon and synthesized mesoporous SBA-15 with BET surface areas of 1030 m2/g and approximately 800 m2/g, respectively. It was demonstrated that the efficiency of MOF-808 in trapping anionic dyes in water was significantly higher while carbon and silica materials exhibited better performances for the case of cationic dyes.