PH-dependent synthesis of two three-dimensional cobalt-based metal organic frameworks with antibacterial activity and dye adsorption

Abstract

Two Co-based metal organic frameworks (MOFs), namely, {Co(Hin)2}n·DMF (1) and {Co2(Hin)4}n (2) (Hin = isonicotinic acid), are solvothermally synthesized from the reaction of isonicotinic acid and cobalt chloride under different pH conditions. Interestingly, both complexes are constructed under acidic conditions, and complex 2 can be fabricated at a lower pH value. Both complexes are characterized by IR spectroscopy, elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The single crystal X-ray diffraction studies indicate that complex 1 and complex 2 are three-dimensional frameworks. The antibacterial activities of complex 1 and complex 2 are investigated by determining their minimal inhibitory concentration (MIC) values against gram-positive bacteria (Staphylococcus. aureus) and gram-negative bacteria (Escherichia. coli), which are bacteria commonly encountered in our daily environments. The results reveal that both complexes are more sensitive to S. aureus than to E. coli. Furthermore, the dye adsorption capacities of complex 1 and complex 2 are investigated. The common organic dyes Congo red and Orange IV are chosen to be absorbed by the title complexes. The results show that both complex 1 and complex 2 have strong absorption capacities toward Orange IV within a short time.