Electrodeposition of Zn-Co-Terephthalate MOF and Its Conversion to Co-Doped ZnO Thin Films

Doping of transition metals to zinc oxide (ZnO) is of great interest for its functionalization as magnetic semiconductor and electrocatalyst. In this study, electrodeposition of metal organic framework (MOF) thin films, in which zinc and cobalt ions are bridged by terephthalic acid (TPA), was made possible by adding TPA to an O-2-saturated aqueous solution containing ZnCl2 and CoCl2. The resulting Zn-Co-TPA MOF was converted to a Co-doped ZnO thin film by annealing at 450 degrees C to burn away TPA and promote crystallization. Simple mixture of ZnCl2 and CoCl2 without TPA resulted in electrodeposition of Co2Cl(OH)(3) along with ZnO, proving usefulness of TPA to blend Zn2+ and Co2+ ions having largely different solubilities and reduction potentials. The maximum achievable doping concentration was about 8%, because excessive addition of CoCl2 resulted in electrodeposition of metallic Co.