The Co‐UMO‐1 Metal Organic Framework: Solvothermal Synthesis of [Co₃{μ₃‐O}₂(C₁₄H₈O₆S)₂(H₂O)₃(C₂H₅OH)] ⋅ 2H₂O, Characterizations, and Application in Methylene Blue Removal

Abstract

The new Co‐based MOF (also called Co‐UMO‐1 MOF with structure of [Co3{μ3‐O}2(C14H8O6S)2(H2O)3(C2H5OH)] ⋅ 2H2O) is solvothermally synthesized in a mixture of water and ethanol at 170 °C for 3 days. The as‐recovered pink‐colored stick‐like crystals crystallizes in the monoclinic crystal system P21/c (n° 13), which consists of three crystallographically independent Co(II) elements that adopt the octahedral coordination geometry. The MOF was also successfully characterized by FTIR, SEM, BET, Zeta potential and UV‐Vis spectroscopy, as well as TG and DSC analyses. At pH 7 and 25 °C, Co‐UMO‐1 MOF shows the maximum of its capacity of adsorption (31.5 mgr gr−1) of the methylene blue (MB) dye, which corresponds to an adsorption efficiency of 79 %. The adsorption of MB follows the pseudo‐second order kinetic model, and occurs via the formation of a monolayer onto the surface of the MOF, in line with the Langmuir isotherm model. Adsorption efficiencies higher than 79 % have not been achieved with Co‐UMO‐1 MOF because of electrostatic interactions between the MOF surface and the MB molecules, which has been confirmed by the Temkin isotherm model. In the aforementioned conditions, Co‐UMO‐1 MOF can be reused after regeneration, showing an adsorption efficiency of 76.2 % after five cycles, which is a promising result.