Synthesis and characterization of metal–organic frameworks fabricated by microwave-assisted ball milling for adsorptive removal of Congo red from aqueous solutions

Abstract

In this study, four metal–organic frameworks (MOFs) were prepared using a simple, low-cost, and high-efficiency technique utilizing simple carboxylic acids (1,3,5-benzenetricarboxylic acid and terephthalic acid) and metal salts (copper(II) acetate tetrahydrate and cobalt(II) acetate tetrahydrate) and microwave-assisted ball milling. The MOFs were characterized by infrared spectrometry, X-ray diffraction, scanning electron microscopy, and thermogravimetry. They were investigated for use as adsorbents for the adsorption of Congo red (CR) from aqueous solutions. The results showed that the adsorption capacity of MOF-2—synthesized from trimesic acid and cobalt(II) acetate tetrahydrate—was the highest, reaching 85.54% after 300 min. Electrostatic and π–π stacking interactions are thought to play an important role in the adsorption of CR onto the MOFs. This MOF material reported in this work demonstrates a superior dye adsorption capacity when compared to other adsorbents.