New interpenetrated mixed (Co/Ni) metal–organic framework for dye removal under mild conditions

Abstract

A new three-dimensional (3D) bimetallic metal–organic framework (MOF), [CoNi(μ3-tp)2(μ2-pyz)2] (1) (tp=terephthalic acid and pyz=pyrazine), was hydrothermally synthesized using mixed O- and N-donor ligands. The structure of 1 has been determined by single-crystal X-ray diffraction analysis and characterized by FT-IR, powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Crystal structure shows that the metal centers are equally occupied by Co2+ and Ni2+ ions that was also confirmed by ICP technique. Two different coordination modes of terephthalate linkers connect three metal centers (CoNi), forming a (4,4)-connected 2D layers, which are pillaring by pyrazine ligands to form an interlocked 3D structure. Topological studies show a uninodal twofold interpenetrated structure with 3(412·63) topological network. The prepared bimetallic MOF was applied as catalyst for the removal of Bismarck brown as a diazo dye under mild conditions. The results showed that compound 1 had good activity and stability during the dye removal process and could be recovered and reused at least for three cycles without considerable loss of activity.