Simultaneous Multi-dye Adsorption using MTV-MOFs Composed of Organic Ligands with Different Properties

It is important to efficiently remove the dyes from wastewater that are widely used in everyday life. Metal-organic frameworks (MOFs) have been investigated as potential dye-adsorbing materials. However, due to their high selectivity, it has been challenging to simultaneously adsorb substances with diverse properties. The present research focuses on MOFs with multiple ligands introduced into a single crystal, known as MTV-MOFs. To achieve the adsorption of various types of dyes simultaneously, two different chemical properties of ligands were mixed to construct the MTV-MOFs. We selected UiO-66 composed of Zr ions with high water resistance, and we succeeded in synthesizing UiO-66-NH2OH by using terephthalic acid with amino groups (bdc-NH2) and hydroxy groups (bdc-OH) at any ratio of the two ligands. The efficacy of MTV-MOF in enhancing the adsorption rate (k2) and adsorbed amount of anionic dyes (methyl orange (MO) and acid green (AG)) and cationic dye (crystal violet (CV)) was demonstrated through adsorption experiments. Additionally, it was observed that the adsorption rate of all three mixed dyes was enhanced in UiO-66-NH2OH-4 (x = 0.14 (x = bdc-NH2/(bdc-NH2 + bdc-OH)). This study is the first examination of dye adsorption utilizing MTV-MOF, and it has been demonstrated that MTV-MOF is efficacious in the removal of a range of noxious substances from aqueous solutions.